Hi,
I think you could get a better deal, tbh. We've just bought a 50K mile, 53 plate renault laguna estate for £2,400 so have a look around...
Anyway, the RAC will provide a mechanic to meet you there to look at the car - google them, I think the AA also offer this service. Or you could get in touch with a mechanic in the area, but I don't know what type of garranty they offer which the RAC or AA could offer.
You must check that you are insured on that person's policy 3rd party at the least. If you're not, then ask that they put you on the insurance and listen to them do it (it's really easy to do that over the telephone and what we did to drive the car we recently bought home before checking out other offers on the net). If you like, get the details of the car and owner and ring up an insurance company and see if they could insure you for the day (fully comp is better) but they might not do this...
You should also consider getting a HPI check done on the car, google it and you'll see what you need from their website.
When you buy the car, or if!, you need the seller to sign the V5 document (usually they send it off, but I would prefer for me to do this as I trust me!). You'll see a space at the bottom in red where he signs and dates. You need both sides of the V5 doc. You complete new details of new owner and send to DVLA.
Obviously you'll need to check out the logbook, but if he's had it since new and you trust him it should be ok.
Erm, trying to think of other things...having just been through this ourselves!
If you can't ensure that you are insured then perhaps you could drive it on private property so you're not as open to hitting other people!! Or having someone hit you.
Good luck with it!
C.