Do what you need ........only!
First forget the GCSE Maths & Physics............ You have bigger fish to fry!
There is nothing particularly hard about the ATPL exams the problem is volume so cluttering your head with GCSE's in not needed.
Training in the USA is not as cheap as you might think, by the time airline tickets, medical insurance, accomodation and car hire are taken into account the price creeps up.
The big problem is that training in Florida won't equipe you to fly in europe so I would guess that you would need 5-10 hours training in the UK before anyone will rent you an aircraft, this of course needs to be included in the Florida PPL price to make a realistic costing. Only then can you decide if it is cheaper in the USA.
Once you have the PPL I can help you with hours building at a total cost that is the same as the USA ( and sometimes cheaper) but with less risk being out of pocket at the end of the deal.