see Fast ford this month. Got what to look for i think. Just make sure you do a HPI check, and if you like the car and feel semi confident its the car for you, then get an AA check just for confidence. Think that gives you some sort of cover that if the car is a nail, then the AA will sort you out.(Don't quote me on that, may need to check with them on that one)

Look for rust around rear arches, rear chassis rails, front cross member, front suspension top mounts, especially if its had a strut brace, good old battery tray area and anywhere that will hold the dirt.

As for the engine, he should have receipts to prove he's bought the parts. Ask to see the car starting from cold and stand by the exhaust to see if any smoke comes out.