BACKYARD INVENTORS; In Britain: a state-aided tradition

The British, like Americans, have a passion for inventing - there is even a government organization to encourage it. Some of their recent inventions are now in use on both sides of the Atlantic.

Ronald Hickman claims he has given men what Isaac Singer gave women with his home sewing machine.

Mr. Hickman is the inventor of the Workmate, a portable home workbench that combines ''a vise and sawhorse all in one.'' Over 10 million have been sold so far in Britain, the United States, and elsewhere - undoubtedly to hammer-wielding women as well as men. But for Hickman, hitting upon the idea was perhaps the easiest part; building it into a success was a long, difficult project.

It all started in 1961, when he inadvertently sawed into a chair he was using as a workbench. Staring at what was left of the furniture, he conceived a way to save other home hobbyists similar grief.

Central to Hickman's invention is a working surface that splits right down the middle, forming the jaws of a powerful vise. On some models the surface can be lowered to hold an object at sawhorse level, and the entire unit can be folded flat for easy carrying and storage.

Hickman abandoned his job as design director for a specialty car company to develop his workbench idea. But for an entire decade his efforts to nail down a contract with Britain's do-it-yourself industry proved futile.

As the years went by, he formed his own company and continued his development efforts. Finally, in the early 1970s, an improved design generated greater industry enthusiasm. Black & Decker, a manufacturer that had previously rejected the Workmate, this time competed for and won a license to make it.

Although Hickman happily anticipates a world market for 200 million Workmates , he says he has spent at least $2 million to fight off the competition. His latest and biggest legal battle is against Sears, Roebuck & Co., which now offers a similar ''Companion'' workbench.

Hickman belongs to a tradition of independent invention in Britain that saw perhaps its brightest hour during World War II. In those dark days, British leaders were unusually receptive to any innovations from private citizens or small research groups that might aid the war effort.

Mindful of their useful role, the British government created a public patron for inventors shortly after the war. Called the National Research Development Corporation, its mandate is to ensure ''that a full and proper use is made of British inventions.'' Last year the NRDC invested some (STR)12.5 million ($23.4 million) in promising projects from industry, universities, research establishments, and individuals. (See accompanying story.)

Undoubtedly the most famous NRDC-funded invention is the Hovercraft. The revolutionary boat design was originated by Christopher Cockerell. He proposed trapping a bubble of compressed air beneath a flat-bottom hull, so that the boat would hover on an ''air cushion.''

The former electronics engineer built his first working model of the Hovercraft in 1955, using a couple of food cans borrowed from his wife's pantry. But not until he met with the NRDC three years later could he persuade anyone to help develop it.

Today the NRDC is minority shareholder in an industrial consortium called the British Hovercraft Corporation. Its craft ply the channel between Britain and France, skimming the waves to complete the crossing in half the time taken by the fastest conventional ferries.

Christopher Cockerell was knighted for his achievements in 1969. More recently, another NRDC-funded inventor received a different accolade from Buckingham Palace. The Flexible Diamond Tool Company, headed by Derek Prowse, was awarded a 1981 Queen's Award for Technological Innovation.

Mr. Prowse invented a new kind of industrial tool for cutting metal - longer-lived than conventional tools, yet selling at only a fraction of the price. His biggest market is in North America.

To produce his tools, Prowse takes a mesh of copper wire and presses it into a sheet of polypropylene plastic. This strengthens the plastic but leaves peaks of metal poking out.

Then he electroplates the mesh with nickel, sprinkling diamond dust into the plating bath at the same time. Tiny nodules of nickel grow on the copper peaks. Diamond grit gets trapped in these nodules, anchoring firmly to provide a keen - and exceptionally durable - cutting edge.

Prowse and Cockerell are success stories for the NRDC - but very few inventors who apply to the agency actually receive funding. Too often, even when they have a promising idea, they overvalue its importance and demand full control of any possible commercial venture.

An alternative opportunity for inventors to find a patron appeared three years ago when Lucius Cary launched Venture Capital Report. Month by month Mr. Cary carefully investigates the claims of inventors and other entrepreneurs. If he is satisfied that they have something worthwhile to offer, he writes a report for his magazine about the inventor, his idea, and the kind of financial support he is seeking.

Peter Strong of South Wales recently found a backer in California through one of Cary's reports. Mr. Strong needed to raise about $150,000. His invention is a natty miniature desktop computer terminal for business executives. It takes up little more space than a telephone - but it ''talks'' readily to big computers. In one demonstration, a banker with Bank of America in London found he could talk to his bank's computer in San Francisco ''merely by dialing a telephone number and pressing a few buttons.''

For every strong contender on the British invention scene, however, there are many of more dubious competence. One backyard inventor offered a British oil company his discovery of ''cosmic-zero'' - a factor he said could make windmills keep on turning even when there was no wind. The scientists asked the inventor if he had safeguarded his own interests by applying for patents. The inventor didn't reply. ''I guess he had problems describing it,'' a company official says.

Another scientist for an electrical engineering company, who was bombarded with proposals for perpetual-motion machines and similar ''breakthroughs,'' soon got into the habit of demonstrating with mathematics why they would not work. His equations showed where the inevitable energy losses arose which would eventually bring the machine to a stop.

''They always accepted the maths,'' the scientist observes. ''They probably didn't understand it. But if I just said they were breaking some law of physics, they would not have believed me."