The volatile swings of the world coffee market have resulted in worker layoffs at a major U.S. coffee roasting company and another round of price increases for British consumers.

The General Foods Corp., headquartered in White Plains, N.Y., yesterday admitted that it has had "some layoffs" at all four of its coffee roasting plants because of declining unit sales of coffee.

A spokesman declined to say how many employees had been laid off or for how long.

General Foods has plants in Jacksonville, Fla., Hoboken, N.J., San Leandro, Calif., and Houston, Texas, which process beans for its Maxwell House and Brim labels.

Last week, the corporation revised downward its earlier earnings projection for the first quarter of fiscal 1877 because of shrinking coffee sales.

Meanwhile, British coffee roasters announced yesterday that they will follow General Foods' Maxwell House U.K. lead in raising the price of instant coffee 85 cents per 4-ounce jar.

Shoppers will have to pay $2.89 a jar when this latest - and biggest - increase filters through to the shops in the autumn.

A spokesman for Nestle defended the increase, saying "it's hard for the shoppers to believe, I know, but we have not been making any profit on Nescafe selling at 1.20 pounds ($2.74)."

And as Briton bewail the forthcoming price increases, manufacturers are buying coffee beans much cheaper.

Since March prices have fallen on the London market from more than $6,800 a metric ton to approximately $5,100 per ton.

Recent figures show that shoppers are buying 20 per cent less coffee than a year ago.

But the Nestle spokesman said, "I'm afraid we have got a lot of catching up to do."

"There is always a time lag. The 1.70 pounds ($2.89) autumn price will reflect what we were paying for beans in March when prices on the futures were soaring."

If world prices hold fairly stable, manufacturers predict that this will be the last big increase. Some coffee experts think the retail price could start to fall by the start of 1978.