Only in a "Boyzone" world would a Puddle Jumper operation of 19 seats, with no 'crapper' and no cabin crew, come anywhere close to subsidizing for a B737/A320 sized operation, with 'crappers' and cabin crew, in/out of LGW.
Well they have at least one USP that Heathrow and Gatwick can't offer:
"The airport has facilities to securely store your bicycle."