I can’t comment on the Belfast base aspect. Type rating is an old fashioned bond for 3 years. Expect to fly 700 hours a year, maxed out in summer and quiet in winter, but you will still be on min days off over winter as they’ll stick you on standby everyday.
I would say the rostering practices will be a shock to the system coming from BA. They basically don’t have any. We were always told that the Belfast base was hard to get onto as few people leave it and it isn’t expanding. I think you’re in a difficult position, but feel if you join here as an FO with a view of getting command quickly but then can’t get a command quickly onto the BFS base then you’ll be in a worse position than you are now and wonder why you left.