kikko,
the rumours about no more external recruitment into the LHR fleets has been around for YEARS and YEARS. pay no heed to these rumours.
i seriously, seriously doubt that the company would agree (or even the union insist) to a fixed number of LGW crew being able to transfer to LHR.
the process that VS-LHRCSA mentions above was a 'gentlemans' agreement between the union and the company - it was never signed in blood. and toward the end of EF LGW they only transfered about 20 per year if i recall correctly.
it will purely be a case of putting your name on a transfer list and waiting for a call to offer you your choice of base and/or fleet when a gap in that base/fleet opens up.