Can my employer force me to work on a Bank Holiday even if it is not my usual contracted day to work?

NO. Nobody can be required to work a bank holiday, with certain exceptions such as police officers nurses and firemen. Employers often try this one on. In the Hotel and Catering industry, it is almost standard procedure. Another common ploy is to abuse staff in the reverse direction, ie to give them the bank holiday as their 'day off' to avoid paying them. This is also illegal. Basic rule applies here: IF IT'S A BANK HOLIDAY, EVERYBODY GETS THE DAY OFF, WITH PAY. If you are on a day off anyway, you are given a day in lieu, or paid for the day. Any employer who tells you otherwise is scamming you. They are attempting to deny you a right which men and women fought to get you. Every employer knows the law, some just choose to ignore it, and abuse their staff. Get yourself a union membership, or call in to the CAB.