There are quite a lot of long-haul charter destinations served by European airlines that don’t see UK service. Anyone know Nosy Be in Madagascar or Salalah in Oman?! More still when you add in Central/South American and Caribbean places the Canadians go to like Huatulco in Mexico, Rio Hato in Panama.
There are certainly opportunities for long-haul with standards clearly acceptable that lack competition from BA/VS or those from the Middle East. I suspect part of this not being exploited or at least tried is the conservative psyche of the British package customer (perhaps also older Britains more generally) who aren’t comfortable exploring places ‘off the beaten track’. For this there is evidence, for example Thomas Cook (?) tried Sanya in China and that didn’t last long. Tui’s own routes to Langkawi (Malaysia) and Pho Quoc (Vietnam) didn’t return.
Regional I suspect is harder to make work because the market for package has shrunk and one-stop options are available with KL/EK etc.