Ricardo82 you can enter the US on the waiver scheme if your a British passport holder and you can start the ground school provided you have applied for your TSA clearance,however you cannot start the sim training until you fingerprints have been approved and full TSA clearance has been given. I just been through all this in November. Flight Saftey at Farnborough will do your finger prints think they charged about $150 for doing it but you have to have the prelimary TSA stuff done.
Hope this helps congrats on your first job,remember the following,
It must have been a gust
I'll pick the bill
I really prefer fat chicks
Chicken is my favorite
and of course I don't mind sleeping on the sofa
If you remember them you'll do well! A long with some of the other sensible advice that has been given here.