Just to reiterate. The current situation at BA is such that if you join BA as a DEP and are in your 30's (or older) and you want to go LH then you will most likely remain an FO.
Also I gather that the Bidline system is waited in favour of the top guys that,
leave aside, you can expect to not get a weekend off for a decade or so. This is worth thinking about if you have or plan to have kids.
I only mention the above because they don't necessarily emphasise it enough
when you go through the recruitment process. (at least that was my experience). I also agree that the situation at LGW is not certain.