When i started work in feb 09 I had booked 3 weeks away in feb 10 and asked for this as part of my AL?

when i started in feb 09 I had booked 3 weeks away in feb 10 and asked for this as part of my AL . I have since not taken this AL and this is owed to me. I resigned on 10 dec 09 and gave 1 months notice saying my last working day would be jan 8th 2110. They are now trying to make me take my leave and effectively leave on next thursday lunchtime, is that legal?