Towers, thanks very much for that. Unfortunately it looks like I'll miss out, as I'm locked into departing in Jan. Perhaps a retrospective claim would be the go (fat chance!).
Reference the 3 years, Ozy Rotorhead, I thought that too, but (unless I'm still confused) I think I read advice recently that has it based on your salary when you actually depart, rather than averaging it over the last while.