I'm not on 320 fleet however I recently bid for a block of 6 days off (last month) to get 'home' and ended up with no more than 2 off in a row for my 8 days, making it nigh on impossible to get back. I'd imagine on 320 it would be even harder as they are shorter on crew, purely in the hands of the rostering gods i'm afraid, no guarantees with anything here!
To get back to UK on ID90 business it'll cost you about £260 return obviously cheaper in cattle.