For £15k and to put it in perspective (with it looking almost like new), I think when you compare it to a nearly new euro box at £15k, you probably won't lose much money, and will have something of a rare head turned on the road (if you can keep it in the good condition). So if you have £15k burning a hole, it's not the worst buy. For me though, it could do with a large bore stainless sports exhaust, and a decent stereo plus 14" sub-in-a-box I'm the boot.
Maybe some sill LED disco lighting. Something tasteful to add to the desirability.