Low wages also key; U.K. inventiveness aids rise of high-tech firms and these British companies are making some 'colorful' profits

Dr. Robert Long hopes that many television station artists will want to play with his ''Paint Box.'' But it will cost them about $107,000. The Paint Box is used to ''paint'' electronically. With it, a station artist can quickly create ''fine art'' on the television screen, or retouch a picture, or add graphics and text to a scene with electronic scissors and paste.

Dr. Long, technical director of Micro Consultants Ltd. here, stresses that this new device is not just another video graphics machine. It is, he indicates, a ''second-generation system'' for painting electronically. It employs what could be called a canvas (a touch tablet), a brush (an electronic stylus), paints (area marked with colors), and a mixing palette.

This is a recent product of Quantel Ltd., a company associated with Micro Consultants. Quantel is a major designer and manufacturer of equipment widely used by the world's television broadcasting industry. If your TV picture does something fancy, it's quite likely that a Quantel system is doing it. There is, for example, a system that's able to manipulate television pictures in an infinite variety of ways. They can be made to spin, tumble, rotate, and zoom, with up to five different pictures at once. The picture can be frozen, or moved in slow motion.

During the 1976 Montreal Olympics, it was Quantel equipment that permitted the TV networks to have one camera on the broad scene and a second one producing a close-up of some specific sports action in a small cutout on that screen.

The company has been so successful that it is, according to Dr. Long, ''in a dominant worldwide position,'' enjoys rapid growth, and has always been profitable. Over 90 percent of Quantel's output is exported. Competitors include Nippon Electric Company, Thomson CSF, and Ampex.

The basic technique for Quantel's video tricks is turning the TV signal into digital form. In TV, the picture is formed electronically by an extremely rapid line scanning the screen with great speed. These signals are turned, in effect, into numbers - around 15 million per second.

''That technique has proved very powerful,'' Dr. Long noted. The numbers are manipulated according to a computer program and instructions from the TV studio personnel to perform desired picture changes. This technique is needed just to synchronize a program involving two TV cameras that are not on the same system. Without it, the devices in the two cameras scanning the scene could be at different levels on the screen and when the studio switched from one camera to another, the picture would flop up or down partway.

Micro Consultants uses the same basic ''quantized television'' system for scientific, industrial, and medical applications. It has a device, for instance, that improves the images obtained by electronic microscopes.

Like so many electronics firms, Quantel was started by people with an idea who left another electronic company - in this case, Peter C. Michael and A. Robert Graves, some 15 years ago. In November 1981, their already successful private company was merged into United Engineering Industries and became the largest component of this publicly traded company. Other companies in the group include Link Electronics, which makes color TV cameras and other equipment; Yewlands Engineering, a producer of precision engineering components; Locomotors , making specialized vehicles, such as mobile TV studio units and armored trucks; Link Systems, a maker of medical electronic gear; and Cosworth, famed for its racing engines.

Last year sales of the group totaled about $47.4 million, up from $33.1 million the year before.

As for that Paint Box, Dr. Long sees a potential market of hundreds of units. He expects studios to find it useful for doing artwork at the last minute for news programs and weather maps, for example.