Suspect the Aurigny application for LHR is more to do with protecting their Gatwick operation - if by some miracle slots come up they would rather have them (and if need be move some of their GCI - LGW and the daily Stansted flight) rather than let a rival in and have to compete on the Guernsey - London route.
They were very quiet about anything to do with Heathrow until Flybe announced the Guernsey - Heathrow flight for last summer and then they started applying for their own slots.