Lude Generation

We're looking for a car to take on the Nurburgring Challenge.

There are quite a few options in the UK (even on a budget), but most of them don't seem to have FIA certified fittings (cage, seats etc).
Front or rear wheel drive - it doesn't matter to us - so Civics do just as well as 3 series BMWs.

Any thoughts?

You will have a few options. Look on https://racecarsdirect.com/ as well the crazy expensive cars there are always low priced affordable ones on there too. You might want to look into getting a race prepped mini. In both Engliand and Scotland there are Mini championships and there always seem to be several for sale.