As Mark mentioned, there are pounds printed by the Bank of England, English Pounds, which feature an image of Queen Elizabeth II, and Scottish Pound notes printed by different banks in Scotland, generally more colorful. All are worth the same, and, technically, should be freely accepted by merchants throughout the U.K.
In practice, though, while English pounds are widely accepted in Scotland, Scottish pounds aren’t always cheerfully or immediately accepted in England, so you may need to be assertive and remind people that you have “real” money, as long as they’re Scottish or English pounds.
As mentioned above, save your Euros, or exchange them thru a bank or with another traveler.