Cambelt and tensioners must be changed every 40,000 miles or 4 years, whichever comes first.If there isnt proof that this has been followe, either walk away or reduce your offer by at least£300.
Check for oil in the coolant expansion tank. If its present, probably best to walk away. Its fixeable, but if the car has been driven like that for a while the resultant overheating could have cooked the engine.
Pull as many plugleads as you can get at - 5 out of 6 hopefully and check for oil in there - if present, reduce your offer by at least £150.
Check all the buttons/switches/aircon etc. work as they should.
Check the autobox functions as it should.
Check the front tyres for scrubbing,particularily on the edges.If they are worn unevenly knock off the price off new tyres (say£100 each) plus the cost of wheel alignment - £75.
If you post your approximate location, there may be an OOFer nearby who could help you when viewing cars etc.
If you buy one which has been maintained properly it will probably be very reliable and a joy to own and drive.If you get one which has been neglected it could be a moneypit and give you many headaches.