Maybe a triangular GCI-JER-LHR route would be viable?
In theory perhaps there's enough passengers wanting to travel, but with the restrictions on GCI's runway (ie nothing above a 146 allowed) and GCI pax having to travel via JER, I don't reckon it would get anywhere.
I doubt even old, not bold's robust Channel Islands' airline (indeed not a bad idea in itself) would manage to secure the needed slots at the Golden Runways. There is simply not enough catchment around these parts to warrant a sizable enough airline (GR was
perhaps once upon a time, but the big boys have (and will continue to) taken over).
The only airline I see making a profit to LHR is BA, maybe when runway 3 is open. But with Open Skies taking effect, and in the 'current economic climate' (my god how I hate that phrase) we'll see more and more regional routes axed from LHR and long haul services coming in.
Off to LGW it is then.