Having just returned from doing the same thing, you need to also consider:
airport transfers to flight school
car hire whilst at flight school - some are nowhere near the training airfield
US compliance costs e.g fingerprinting
calls to home - these can be expensive if you're not careful
cost of maps - you won't have the need for the US ones once you're done but still have to buy the UK ones
Cost of medical & RT prctical tests - you won't need the US ones once you're done but will still need the UK ones if you train in the US i.e. you will pay twice
Hope this helps.
PS - I went to Fort Pierce - great place & great people