
Can't help with airline recommendations or costs but I do know that it's far cheaper to fly to Schiphol say than direct into the UK, avoiding our astronomical handling fees (£200 - £500!).
IIRC you're in Scotland aren't you? You might consider the Harwich to Hook ferry, it takes a lot out of the driving (obviously depending which airport you're flying into), their dog facilities are fantastic and you could get a sleep overnight (you can watch pup on the monitor in your room and visit as often as you like). A good sleep means an easier drive home without having to stop anywhere else overnight.
Edited to say I've use the H2H Stena ferry often with the dogs, while collecting a new puppy and to shows on the continent and I really like it.
Here's my puppy in the small dog kennels, and
exploring the room, and the
exercise area on deck.