A bank account sort code is a number used by banks based in the United Kingdom to identify which bank the account is handled by. Though you could go into your local branch and ask the teller to print out a statement and point out your sort code for you, it is far simpler to simply find it on your debit card.
Look at the right hand side of the front of your card.
Locate the 8 digit set of numbers. This is your account number.
Locate the three pairs of numbers, separated by dashes, immediately to the left of your account number. This is your bank sorting code.