Nobody knows! Really, nobody knows, even Britannia management. Anybody on the line tells you that they know should be treated with some suspicion. The winter establishment will be driven by the volume of flying, both inhouse and third party. Other factors that might affect it will include things like how busy LBA will be in the winter (and other non LGW & MAN bases), the possibility of further adjustments to the tailored crew compliment process, the possibility of double PMI (or three sector) rosters, the possibility of a restructuring of the onboard rank structure and last but not least, the results of the CRC requirement: This last is also partly why so many late courses are being run - the company is concerned that there will be at least some staff losses as a result of CRC.
As Balboy says, fingers crossed for you.