it is surprising that they've kept GLA, EDI and CDG
Yes, that really surprises me also. Our loads are often terrible on GLA / EDI, yet they've been pretty good on MXP / MUC. OK, I don't know what the yields are, but it seems to me that the routes with no competition have been cut & routes left can be dominated by easyJet.
The cynic in me thinks that the slots are to be used for Flybe approved airports, not BRS. And cancelling routes already served by another airline doesn't attract bad press - BA gets the rap for the current route cancellations, Flybe are squeaky clean for the future ones.