The best P plate car is not the one with the most power, so that you can introduce the rear of it to every gutter and front yard of every home in your street; as you live out your initial D fantasies, with your lowest common denominator skillset.
The best P plate car is the one that allows you to get off your P's with your license intact, you and your mates all still alive, and with the bare minimum of accidents due to aforementioned lack of skills.
Get something cheap, light, moderately powered and fun to drive, then spend some money actually LEARNING how to drive properly on track, so that you can make the most of a decent car; once you have matured a little and learned how to properly assess and manage risk, and the pressure of your peers.
You don't want the first mistake you make (and I promise, you will), to be your last.