Ok Apaddy, I always think these things are worth a try!
And cabincrewmember, i've not heard of anyone doing that the way you describe. As far as I know if you do that you will have to leave ba in order to come in again at the bottom of the pile at LHR, not only with your crew date but also with your company date of joining.
I think its sad that people who are just joining are already working out how to transfer out of LGW. Its a great place to work and you might well enjoy it, but i'd question why you or anyone who wants to be at LHR that badly would join LGW in the first place?