Cheers everyone for the advice/assistance.
Got there - delayed, but got there. Meant we could do everything we wanted though.
Just annoyed at BA giving weaselly excuses. Even on the way back we were delayed boarding because of "re-de-icing" - when you could clearly see they weren't de-icing the plane. The de-icing took all of 15minutes after we were on board. So why not jsut tell us they were waiting for a de-icing slot, or whatever the real reason was, with an expected delay time - we could have wandered round the shops for an extra hour.....