I'd like it support everything FBW has said and maybe add a a couple of things.
Firstly I understand everyone's eagerness to get to WWLHR for one reason or another i.e. wanting to commute from one far away place or another, or you want to see the world, or you've heard the pay is better etc etc, I could go on....
The reality as FBW has stated is that the world and his wife want to be WWLHR and the list no matter where you start in BA is long, and as new joiners you will be at the bottom.
It is an uncertain time at LGW at the moment but I am in no doubt that it will be sorted one way or another and there will be some sort of arrangement to transfer to LHR.
But PLEASE.... LGW is a great place to work. Many of us have had the opportunity to transfer to LHR (all my training course are now WWLHR) but we have stayed beacause we enjoy the family atmosphere of a small base and the social side that results. Plus promotion is very swift at LGW, and promises to be even swifter with this midfleet proposal, so those with experience may find themselves in a very good postition.
Never forget that if you do get BA there are plenty that didn't, so be proud that you've got in no matter what base you get sent to. It's still the benchmark for crew T&C's in the UK.
Hope this clarifies some things for all our there. Hopefully see you soon! (I could be training you!)