Half of (48 per cent) British motorists believe they've been scammed by a car mechanic, costing the nation ￡8 billion in over charged, unnecessary or poor quality work, according to research from insurance.co.uk.A third of these (34 per cent) believe they've been fiddled for ￡100, more than half (51 per cent) think they've overpaid by ￡500, one in ten (12 per cent) think their bills have been stretched by an additional ￡1000 and 3 per cent say they've been stung for a whopping ￡3000.Whilst 3 in 5 drivers (57 per cent) would always take their car to a garage for maintenance and servicing, a little over a third (38 per cent) would only take their car to a professional if it needed major maintenance work and 1 in 20 (5 per cent) say that they never take their car to a garage, preferring to do the job themselves.Fifty two per cent opt to stay away from professional mechanics, for fear of being overcharged for repairs or servicing, while 48 per cent believe a garage will try to do more work than is actually necessary and 34 per cent (22 per cent of men, 42 per cent of women) fear their lack of knowledge about cars will be exploited. The research reveals our concerns about trades people are not restricted to overpriced work - a quarter of car owners (28 per cent) question the quality of the work they've received from a mechanic, garage or workshop.Steve Grainger, head of insurance.co.uk, said: 'Whilst the vast majority of car mechanics and garages are entirely reputable, our research highlights that there are a number of rogue tradesmen trying to exploit drivers and consumer confidence in the industry is low.'In the current economic climate car owners could be holding on to used cars for longer, rather than trading in for a new model. For the safety of all road users, it's vital we make sure our vehicles are adequately maintained and serviced. To offer customers peace of mind and to make sure they get a fair deal from a trusted garage in their area, anyone comparing car insurance policies through insurance.co.uk between August and November will get free membership to the National Service Network (NSN)'.Top 3 tips for car owners:Use a garage you can trust, recommended either by a friend, trade body or approved network Don't be afraid to say 'no' and get a second opinion Ask for a breakdown of the bill and make sure things have been done - if necessary, ask the mechanic to show you what they've done