Although there is no automatic right not to work on Christmas Day, most people have the right to either time off or extra pay on Christmas Day through their contract with their employer. Even when entitlements of this nature are not explicitly written down, they may sometimes be incorporated by 'custom and practice' (for example, where they have become part of the customary terms of employment in a particular industry). These rights have come about largely because of the work of trade unions.
Check your contract to see if it specifies whether you have the right to take bank holidays off. By law, you must be given a written statement of the terms of your contract within eight weeks of starting work. Your contract may also say something about when you may be required to work overtime. Once you have checked your contract, go and see your union rep.
The Christmas Trading Act 2004 prohibits most large retail stores from opening on Christmas Day.