Rachel Ward was in England Sunday night, long before the first frame of "The Thorn Birds," ABC's 10 hours of televised high melodrama, hit the picture tube. She wanted to be sure she wouldn't see herself starring in it.

She never watched dailies during the six months of shooting. She even leaves the ABC screening room, where she has been enduring interviews, before a publicist can crank up a videotape for the press to sample. "I feel very vulnerable about it all," she says.

Though she's tuning out, Rachel Ward is likely to draw a thousand hopeful actresses' envy and outrage like an electromagnet.

She's genuinely stunning, even in deliberately antistarlet dress like the chambray shirt, patchwork skirt, cowboy boots and post-punk haircut in which she's been traipsing across town promoting "The Thorn Birds" (which continues tonight at 9 on Channel 7). She's brainy and articulate. She hasn't had to struggle to lose a twang or drawl, her native accent being an elegant Oxfordshire in which that elongated yellow fruit becomes a "banahnah." In fact, she hasn't had to struggle much at all. The chance to star as Richard Chamberlain's seductress, to make the cover of People--fame and good fortune seem to be falling, dues unpaid, into her lap.

Plus, the minor complication of falling in love with her craggy co-star, Australian actor Bryan Brown, who also starred in "Breaker Morant." They'll be married next month in England, and Ward will wear the lacy Edwardian dress she found in a Manhattan antique shop between interviews.

"I often feel like there's a brick hanging above my head by a thread, and the thread's getting thinner and thinner and one day, all the things that have come easy will crash--kaBONK--on my head," Ward worries. Sprawling on a sofa in the screening room, she looks as though she'd like a cigarette if she hadn't quit smoking and turned into a vegetarian/meditation/aerobics fiend while in training to play "Thorn Birds" heroine Meggie Cleary. She indulges in a chocolate chip cookie instead.

"Maybe it is a requirement for an actress to go through miserable times. I've never known what it is to experience extreme poverty, to not have a friend in the world."

Ward can hear the accusation already: she hasn't suffered.

"But another part of me says they didn't have to choose me," she adds, stoking her self-confidence. She is constantly advising herself to Be Positive, Be Positive. "I've auditioned for everything I've gotten. Other people were competing. I must be doing something."

One could hardly blame those who wait tables by night and haunt cattle calls by day for grumbling. "I enjoy my life," Ward confesses. "Everything has been wonderful and everything has been easy." Her parents, landed gentlefolk in an English village called Chipping Norton, gave her "an idyllic child's life": horses and an estate to ride them across, money for "movies and a good dentist." She can't even tell the grumblers that she turned to show biz to compensate for being neglected at home. "None of that, no. I didn't particularly want for anything."

Sixteen and bored, she drifted to Paris, then to art school and fell into modeling. Within a few years, she was in New York shooting Cosmo covers, touring the discos and wandering "in a floaty gown" through Lincoln-Mercury commercials when Burt Reynolds cast her as his leading lady in "Sharky's Machine" in 1980. Next came "Dead Men Don't Wear Plaid" with Steve Martin and then, this mega-role.

Becoming Meggie Cleary was Rachel Ward's most arduous undertaking. She botched her first reading, distracted by the prospect of another film offer, and the producers let her agent know there wouldn't be a second reading. Suddenly, it mattered. "Say anything, say I was ill, see if they'll have me back," she instructed her agent. Ward then signed on with drama coach Sondra Seacat, whose clients include Jessica Lange and Mickey Rourke of "Diner." ("Maybe I should keep quiet about it," Ward giggles. "Maybe I'm not going to do Sondra's reputation any good.") But after five intensive days of study she did a screen test and got the part.

Despite the fitness campaign Ward waged before the filming began, "The Thorn Birds" wore her out. It was a 90-minute commute from her house near Mulholland Drive in L.A. to the dry, dusty, fly-ridden Simi Valley where the production designer had constructed an Australian sheep ranch. Toward the end of the project, which called for Ward to age 23 years between the first and final episodes, the hours spent at the hands of make-up artists meant that she had to get out of bed at 3 a.m. to be on the set by 7:30. Playing Meggie through one tragedy after another eroded the energy she'd tried to stockpile. Rumors of squabbles among the cast, though not confirmed by the principals, percolated into the gossip columns. After the wrap in November, she retreated to Chipping Norton for rest and pampering. "It just isn't a role you can walk through," she says. "I'm only just filling up again."

Before Seacat's tutelage, Ward thinks, her acting was largely "jumping in, crossing my fingers and hoping it would go all right." Now, though, she has a technique that is "very Method" and "working from the inside out" and "learning about my instrument." She's sure that her professional evolution is there on the screen for all to see, which both gratifies and mortifies.

"I hate everything in the first show; I hope people don't judge my performance by it," she says. The first episode ended with her least favorite scene: The script called for her to rage at Chamberlain, the priest who has rejected her (but is nowhere in sight), vowing "Go on, go on with that God of yours, but you'll come back to me . . . " rather like Scarlett O'Hara swearing never to go hungry again.

Ward shot it four times and still doesn't like the result. "A dramatic little piece," she winces. "I never felt it."

She's much more confident about the episodes to be broadcast tonight and tomorrow night. "The Thorn Birds" was shot mostly in sequence, so that by the last scenes the cast had been working together for almost six months, and Ward had learned that much more about her instrument.

"I only had to look at Richard and amazing things would come; I really felt we'd been through a journey together," Ward remembers. "Toward the end it was really working and I felt great about it."

It was helpful that Ward felt immediately attracted to Brown, who plays Meggie's husband Luke. "Meggie's whole relationship with Luke is a very sexual one, so it was important to me that whoever played Luke be someone I felt was sexy," says Ward. "I was very relieved when I saw Bryan." She is smiling shyly and addressing the ceiling; discussing her courtship discomforts her.

Being actors, though, Ward and Brown used their offscreen chemistry to infuse their performances. "Our real-life romance went along very much at the same pace as the romance in the story," she says. "Bryan was very aware of not getting ahead of the shooting. He never kissed me before he actually kissed me in the film."

Ward and Brown plan to live in Los Angeles and, between jobs, in a beach house outside Sydney, surrounded by parrots and banahnah trees. Diction aside, Ward no longers feels properly British, she says. She likes Australia's wildness--"it's dry, rugged, the opposite of England, so tame and green with its little fences"--but she feels American. "England is a very cerebral kind of country: it's all in their minds and in their wit," she explains. "America comes more from the heart. It's more emotional and I'm more emotional."

One of the things she's emotional about is the performance she refuses to watch but which untold millions will. The vision of that other model-turned-miniseries actress-turned-critic's prey, Ali MacGraw, is too fresh for comfort. "I've really no idea how I'm going to be accepted, how people are going to judge my performance."

Ward has been telling interviewers and herself that this shift from model to actress is really no more traumatic than any one else's career change. But the reviewers, while not being as tough on her as they were on MacGraw, haven't seemed convinced.

"Aww, reviews," Ward groans. "One always has nightmares about everyone saying, 'Argh, worst actress I've ever seen. Just shows that models can't do it.' If one chooses to be in this business, one is vulnerable to that sort of attack. Maybe it's just; maybe it's not. I'd hate to be in that position and I have a lot of fear that I will be . . .

One round of nasty reviews will not send her back to being a sportscar-seller in a floaty gown, Ward vows. But failing to reach her own standards just might. "I know when I'm doing it right, when it works. If I can't get to that place often enough, I don't want to act," she says. "I don't want to be semigood."

And what would she do instead? "Have babies, maybe," she shrugs. "Paint. Anything."