I've already decided that I'll make my own way to Paris, probably Eurostar.
Nothing the UK govt can do to change the behaviour of its citizens once they are outside UK Plc.
Afaik, BA to GCM isn't internal as they aren't treated in same way as French overseas dept. The market to French Caribbean is far too small for anyone to complain!
Yes, Hawaii is where it works in your favour.
Of course, Osbourne has admitted what we've known all along -APD isn't a green tax anyway, it is just a revenue raiser. If they really wanted to modify behaviour, they would tax the other way round, as there are alternatives to some short haul flights - but I think the £26 rtn already penalises UK domestic tourism enough!
I'd look at DUB for the USA - sometimes I've seen flights from there way cheaper than from say MAN - depends on if the airlines think they can get more yield on a direct route. There must be people who fly say BHX with FR, only then to fly DUB-LHR & back over to the USA!