I had this on my dashboard - when I bought my fronty from the garage. The milage was showing 2300, for a T reg!!!
They said it had been clocked, and had no service history. But I had a real good look round and the engine looked brand new, new radiator, new belts etc... and for the price it was it was a bargain.
However when I had paid, they then managed to find the service manual for it - and the previous owner had all the paperwork and it had actually had an engine rebuild from a place in Cardiff for £1,400 and was guarnateed for 12 months! I only paid £1,900 so well worth the money.
Only issue was the rocket cover gasket was leaking and the power steering pipe - which I had done under the 3 month warrenty.
Also the BIG one - was that it had actually only done 87,000 miles -

- the problem was that it had the new B model clocks - which I believe had issues - so I hear they tended to replace the clocks instead of repairing them.
Also the service history was spotless, up to 65,000 is was vauxhall dealer serviced and then every year at local garages.
So I would say, follow your nose - have a good look around! - dont judge a book by its cover!!