Thats odd, it should be, I'm looking at my current account statement and it clearly shows the sort code to the left of the Account number.
If its not there try ringing HSBC the contact number according to my statement is 08457 404404. If the sort code is missing off your account try to explain to them and see if they can rectify it. Whilst you are at it, ask them for the sort code as well.
One other thing if you have a card for the account - it should be on the card as well, its in the format (two numbers - two numbers - two numbers e.g 01-01-01)