If you waste £30,000 on a 420 at 22 then you are completely and utterly mad. Hopefully you'll see sense before then, there is far, far more to life than cars, although cars are awesome, and £30k on something so totally ordinary is something you do when £30k is a trivial amount of money not all the money you have + more.
You are also far more likely to be in a position to buy awesome cars in the future if you don't waste massive, massive amounts of money on totally ordinary cars in the present. £15k Polo at 19 and plans for a £30k 2 litre diesel BMW at 22 is not how you end up with something like gurdas at 25, thats for sure.