It's probably a better/easier idea to talk to PP and see if they can either give you enough to last (if you explain the situation, they might be able to). I haven't had to deal with it yet, but I know other people have mentioned having trouble getting the exact same pills. It seems there's some variation in the formula.
If they do give you a prescription to have filled in a UK pharmacy, I'd ask them to make sure that, in addition to a brand- or generic-name pill, they also specify the exact amounts of the drug combo (i.e. .24 mg norgestimate/.035 ethinyl estradiol), to make it easier for the UK pharmacist to fill if they don't have the same exact pill.