IT'S done and dusted. The

latest vacuum cleaners have been put to the test in households across of the country, and any dirt about them is no longer being swept under the carpet.

Consumer specialist Which? has just published the results of its survey into the machines' all-round performance, and they are certain to be carefully scrutinised by consumers as well

as manufacturers.

Vacuum-cleaning is big business, as the latest list of the nation's top entrepreneurs demonstrates. Inventor James Dyson is worth #100m thanks to his model design.

The machines also appear to have an inspirational element. The idea behind Robot Wars - hailed as the biggest internat-ional spectator sport of the 1990s - was dreamed up thanks to a broken vacuum cleaner. Marc Thorpe, the man behind the creation of Star Wars' R2-D2 character, was repairing his machine when he envisaged what could be done if he mounted a power tool on it and staged a combat event. The dust is history.

It has even been predicted that in the future, vacuum cleaners could be programmed to whirr into action when dust reaches a set level.

Which?, however, concentrated on what the machines are capable of today, and in doing so swept into a row between rival manufacturers.

Last month the revolutionary Dyson company threatened to take legal action against Miele after the German firm published adverts disputing claims that Dyson products had ''100% suction, 100% of the time''.

Miele claimed independent tests proved its own models had up to twice the sucking power of Dyson's which, it said, lost suction as the dust bowls filled up.

Both companies feature strongly in the Which? investigation, which subjected 17 models to a series of rigorous tests, and assessed their performance against 23 different challenges.

Laboratory tests included measuring the volume of dust picked up when the bags are empty and full and how much is blown back out through the exhaust, as well as the quantity of allergens sucked up and retained by the machines.

How easy the machines were to use was another important factor, and the researchers dec-ided the best way to test for ''convenience drawbacks'' was to ask people

to put them through their

paces under everyday conditions.

Thirty-nine took steps to fulfil test conditions of the research which also examined manoeuvrability, noise, and durability.

Top scores in the upright category went to the #200 Dyson DC01 and the same-price Electrolux Power System 1720, which each scooped seven points out of 10. However, a ''best buy'', at only one point below them and at a price of #130, was the Hoover PurePower U3120.

Among cylinder cleaners, the best buys with nine points were the #160 Miele S312i, the #110 Hoover Alpina SC211, and the #150 Panasonic MC-E962, as well as the #80 Morphy Richards Handy 70011, which received eight points. This time round, the two Dyson models lost out to rivals Miele, with the #230 DC02 Absolute and the #200 DC02 rated poorer value for money and scoring eight and seven points respectively.

In the critical dust pick-up test, Dyson again fared worse than Miele whose cylinder model, along with those of Panasonic and Morphy Richards, were all judged to work better.

RESULTS from the ''reliability'' challenge found one in 10 cylinders and one in five uprights needed a repair in the first five years. Miele was the most reliable make of cylinder and AEG and Panasonic the most troublesome. Oreck was the most reliable upright and Kirby models had the most problems.

The investigation was not without difficulties: two upright models - the Hoover Turbopower U1060 and Oreck XL - were withdrawn from tests after

safety problems emerged, though Hoover was taking steps to correct them and Oreck had already modified current production.

News of the Which? tests came as a surprise to the association which represents manufacturers of domestic electrical appliances.

As for giving a breakdown of the UK market share, the association said the manufacturers didn't like to divulge on competition grounds, leaving that question up in the air. Air that depends on which vacuum cleaner you use.