If you look at just how much GIP have spent, you'll realise that there's a danger of uncompetitve charges. It's still mainly TOM/MON/EZY/BA/VS to the sun with DY bigging it up. FR gave up on most sun routes and BE dropped LBA and ABZ. Domestic in particular is a challenge.
I think GIP have an overly optimistic view of what they can sustain at LGW. This is a lesson MAN went through and has adapted well to. Don't marginalise one part of your market through exorbitant fees!