Sinclair Research Ltd., a leading British personal computer company and the corporate brainchild of inventor Clive Sinclair, will be acquired by British media owner Robert Maxwell in a deal valued at about $15.2 million.

The purchase brings together two of Britain's most unusual and best-known businessmen: Maxwell, the outspoken Czechoslovakian emigre' and war hero who has built a multimillion-dollar communications empire in his adopted country, and Sinclair, the balding, bespectacled and entrepreneurial "boffin" who built the world's first under-$100 computer and won the admiration of the conservative Thatcher government plus a knighthood.

The deal, completed this weekend in London, came with Sinclair Research just weeks away from insolvency, according to sources close to the company. As with other computer manufacturers around the world, Sinclair has been badly hurt by a drop in sales.

Last month, cash flow problems caused by excess computer inventory prompted the company to seek a two-month extension on $12 million worth of debt payments to major suppliers Thorn EMI Ltd. and Timex. Sinclair recently was forced to start looking for a new managing director for his company.

Maxwell, the controversial press baron who owns the London tabloid Daily Mirror, reportedly agreed this past weekend to have his Hollis Bros. subsidiary purchase a major share of Clive Sinclair's 85 percent holding in Sinclair Research. A special stock issue would give Maxwell a 75 percent effective stake in the computer company.

According to a Maxwell spokesman, Sinclair will be a "life president" of the company "but he won't have an executive position." Maxwell is looking for a new managing director for the company.

Maxwell "believes in Sir Clive's inventive genius," said the spokesman, "but he's failed in the past because he doesn't understand commercial marketing things."

Sinclair, a technical journalist who never went to college, made his reputation in the early 1970s by designing and selling some of the first pocket calculators and digital watches. The Sinclair ZX80 and ZX81 computers that sold for under $100 each helped transform his company into a profitable multimillion-dollar British high technology leader. However, the recently launched QL (for Quantum Leap) machine has sold in the tens of thousands rather than the anticipated hundreds of thousands. In addition, says the Maxwell spokesman, "there are overstocks of $42 million worth of unsold computers" in Sinclair Research Ltd. warehouses.

The spokesman said that Maxwell may seek to sell those computers to Russia and Bulgaria, export regulations permitting.

Maxwell is chairman of Pergamon Press Ltd., The British Printing & Communication Corp., Mirror Group Newspapers and Rediffusion Cablevision, Britain's largest cable television company.