most people would take their test in the driving schoolcar tehy've been learning in. A lot of examiners don't like to sit in cars without dual control just in case
Anything old, small and common will do, especially when you are a young male new driver! When I first passed my test the AA quoted me £750 to insure a 15 year old nissan micra 3rd party! I found it cheaper elsewhere, but it was still over £500 at the time
until recently I've always had 1.1l cars (micras, metros, clios, polos) and all have been fine. I never spent more than £800 on one and they normally lasted me a couple of years or so. Get something with as lnog an mot and tax as possible, that way if you spend £500 on a car and run it into the ground then you won't want to try gettin it through an mot in 10 months time