Nice to see you have a sense of humour.
Check internal roof lining for footprints, if you find any could be your type of car.
Sorry, right serious now.
Stay away from car supermarkets, they are expert con artists.
I've found over the years that established second hand car dealers are far more honest than joe public.
Always use Parkers to check the price and opinions - and believe what they say.
http://www.parkers.co.uk/#
Basic engine check - after smooth talking salesman has driven a few miles ie engine is hot - get out of car, look at exhaust pipe and tell wonder boy to stamp on the accelerator pedal, if he does'nt stamp on the pedal the engine is knackered, if he does it and you see smoke - even a teeny weeny bit the engine is knackered.
To check clutch - put in second gear - apply hand brake very firmly - slowly accelerate while letting out clutch - try to balance clutch and accelerator to prevent the engine stalling , if you end up with foot off clutch and engine running, clutch is knackered.
Gear box check, engine off, foot on clutch, gear change should be silky smooth - no jerks, excessive force or hesitation, the feel of the gear change should be the same for all gears.
Steering check, put on full lock and slowly drive in a circle going up and down a kerb - if you hear a knocking sound, steering is knackered.
Wheel bearing check - grip front wheel at 3 and 9 o clock and try to shake from side to side, if you hear a noise or clonking its knackered.
Ask friends and family if they know of a reliable honest mechanic and seek his help, they do exist. Perhaps search a local forum.
Good luck