G of G
Normally after any conversion in BA, by any pilot, there is a full time requirement for a modest period. (I think 3 months...) Not sure whether new joiners would need to fulfill a complete year or not. It absolutely wont be a problem to ask, either before, or during interview. BA is an enlightened employer, everyone understands the need for PTWK! you won't be marked down for LMF!
The only thing I didn't mention, is that it is a permanent change to your contract. ie No guarantee you can ever revert to full time! So 'buyer beware'!