Depends really. I went for a Class 2 initially, then upgraded to a Class 1 when I needed it. Then again, when I did my PPL I had no intention of going any further.
If your aim is to go pro, it could well be worth getting the Class 1 from the outset, then at least you know there's nothing to bite you when the time comes. That said, it's not the mountain some make it out to be. If you're in good health (which you should be at 16), and can see and hear properly you'll breeze through it. In your situation I'd be tempted to just get the Class 2, then upgrade as/when neccessary. It would certainly save you going to Gatwick, and probably knocking on a couple of hundred quid.