it depends on how/where you change up your money.
personally i just use ATM's and get a better exchange rate than using cash.
the only exception to this is when buying ciggies/tobacco when most tabacs will give you an exchange rate about 3 cents above the current tourist rate for english money (sorry cidermonster, i've never tried to use scottish money so i don't know about that

)
there is no real difference between buying in the uk or in the resort. just make sure you have some euros for any initial expenses when you arrive like deposits for rooms/room safes/tv/first nights booze etc