Take a little time to do some research as it will inevitably ensure that you are not parted from a significant wedge of your hard earned cash. By this I mean:-
- go onto the UK CAA website. Search for a current list of approved schools. That way you will be forearmed and can sort the wheat from the chaff when some marketing guru tries to sell you a "JAA product" when in fact it ain't
- while there download a copy of LASORS. Then have a read and see what you are in for along the way ie: PPL/ME/CPL/IR requirements, number of hours etc etc.
- read the stickys at the top of this forum. Training in the US has been discussed about a million times over the years and all the information you could ever want is there including which schools are cr*p, which are okay and which are great
- Search on the private flying forum for undertaking a PPL in the US. Most PPL stuff is discussed in that forum rather than this one.
Good luck.
PS: Drop the use of the term "British ATPL". What you are after is a JAA CPL with a multi engine rating and instrument rating. It is commonly referred to as a frozen ATPL but this term has no legal meaning. If you want your licence to be issued by the UK CAA (in Gatwick) then you must jump through their hoops.