Just to back up Kempie:
Public holidays have no legal status in regard to employment laws. (The only exception is that employees in the banking sector do have 'bank holidays', which form some of our 'public holidays', enshrined in law). If you normally work on a Friday, your employer has the right to insist that you work on Boxing Day, at your normal pay rate. (Many employers choose to pay more but there is no obligation for them to do so unless your contract specifies otherwise).
Similarly, if your business was open on Christmas Day (and you normally work on Thursdays) your employer could require to to work, as usual, for normal pay.
Chris
PS: As an aside, you might be interested in my experiences of working on Christmas Day, for normal pay, which I related in my post here ;-)
http://www.theanswerbank.co.uk/Seasonal/Christ mas/Question325808.html