Thanks very much for the replies!

I will definitely let you know how the charter flight goes if that does work out. From speaking with a few jet companies, it sounds like there is a fair bit of interest from people travelling with pets, either because their dogs aren't allowed on a commercial flight due to the breed (pugs, etc) or because they just want a less stressful option than the cargo hold. One company is even thinking of setting up a monthly pet flight from UK to US, which would be great - with a full flight, chartering is actually reasonably economical. Anyway, I'll let you know what I find out!

In terms of flying with my dog in cabin, he's 35kg/70lbs, so unfortunately too big to go under the seat I've not seen any airlines that allow a larger dog in the cabin, so I think my only option on commercial flights would be for him to go in a travel crate in the cargo hold, which I don't think would work very well for my dog. Thank you for the suggestion, though!

Thank you again for the replies and I will let you know how it goes!
Karina