Hi,
Although some prices for various elements to do with eyecare and glasses/lenses etc have come down a little in the UK, the USA remains cheaper often significantly, for the exact same product and therefore I'd suggest you get your glasses made up there in order to save some money.
However, as per above, if you do find yourself needing to have glasses made here, then yes, the prescription should be able to be processed here in the UK
Cheers, DtM! West London & Slough UK!