Hello and
As DoggyRev said ,you should be able to pick one up for your budget, but will be looking at earlier, higher mileage cars. But don't let the mileage be a deciding factor. If a car has been looked after and serviced regularly, high mileage isn't a huge issue. But for sub £5k, you are at the lower end of the market.
Have a read through here: http://www.350z-uk.com/topic/56870-guide-for-new-memberspotential-buyers/
Good luck with the search.