HSBC is the name of the bank. GBP is an abbreviation for British Pounds (hopefully you know what those are).

HSBC has something called an offshore account. The difference between this type of account and a student account that you'd set up when you got to England is that a) it's much easier to setup, with a lot fewer requirements (the only real requirement is a minimum deposit of 5,000 pounds, or about 9,000 dollars). When you're done with the account, you can always withdraw them back to your US account.

When you open the Amex card, you can set it up so that when you get your bill, you don't have to write a check, but it automatically subtracts whatever you owe from this bank account.

Trust me, for what you want to do, this is definitely the way to do it.