As Ethel and dzug have said, you must first look on your contract of employment. This will spell out exactly what your holiday entitlement is, and whether you will be expected to be available for work on bank or public holidays.
(NOTE: Christmas Day is not a bank holiday in England and Wales; it is a public holiday in common law, as is Good Friday).
Thank you for your answers, I'm still a bit confused, if Xmas day is a public holiday, then where does the 8 Bank Holidays come in ?
It says nothing about Xmas on my contract though only that I'm entitled to 8 Bank Holidays.