Seems like a lot of money to me. If you did end up going for it you should definately get them to tax and service it. HPI and RAC check would'nt cost too much to do on a private sale. You did'nt say what year the car is, but nearly £6k is alot of money. Also if you could insure it, that sort of money would get you into Turbo or 1.8 20Valve territory.
Just realised you put the year of the car in the title!..D'oh.
I did a quick search on the Autotrader website. found the following if you need low insurance:
1) 2002 1.4s 51,000 miles FSH etc, etc £5,400.00 (still think thats expensive!!)
2) 2002 1.4s 41,000 miles " " £5,500.00
and if you use the money you save buying private, and not paying salesmans wages you could get
a 2001 2.0 GTI with all the kit (climate, centre armrest CD player etc) 36,000 £5,950.
Keep on looking around if I were you.