My advice? Save it.
You are statistically far more likely to have a crash in the first two years of driving - not necessarily because you're a bad driver, but maybe because you are not experienced enough to spot and avoid other bad drivers on the road. Give yourself 2 years driving a car that you wouldn't mind losing if it got written off by some idiot.
Buy something that's affordable, dependable, and reliable to get you through the first two years - after which I'd recommend steady increases in power (double the BHP each time should be more than enough) so if you've got a 80bhp car for the first two years, get one that's around 160bhp and learn how to handle that extra power. If you go flat out and buy a 500bhp Skyline you're going to wrap it up on the first bend you come to - they're rear wheel drive and very unforgiving if you happen to lose traction at any point - and it's easy to do in a car like that - not to mention the 15mpg average on fuel economy.
Remember that Britain's roads aren't made for fast cars. Limited to 70mph (which any modern 1 litre engined car can do with relative ease) and even less if you're not on a dual carriageway, your 0-60 time will be the only difference to your overall journey time, and that's likely to make you a few minutes later on a long journey.
Modified cars aren't the way forward, either. British laws are becoming more and more strict and the Police are clamping down on modified meets. As a member of the modified scene since 2009, I can tell you it's gone downhill fast and you'll be very lucky if you can enjoy any modified luxuries when you finally pass your test in 2 years time. Remember that every modification - whether it affects the car's drive-ability in any way - must be declared to your insurance and very few insurers will touch a car with power-enhancing mods - especially with you being so young.
To summarise: buy something cheap as your first car, and try to keep it for 2 years. In that time you will find a world of other cars and many will take your fancy. There is no one "best car in the world" for everyone - find what you like, drive all that you can afford, and pick the one(s) you like best.
~Matt