Hi
We brought our dog and car over.
The ferry/car route is a long journey but you are in charge of your pet pretty much all the time. We came via the Portsmouth/Bilbao route and you can visit your pet at anytime during the trip (they even have pet friendly cabins - but very limited numbers).
Unfortunately I've no experience of flying with a pet but a good place to start is the defra website
Defra - Department for Environment, Food and Rural Affairs - this gives you all the up-to-date / legal requirements for travellling with your pet. Plus information on authorised routes and carries.
Whatever you do don't delay starting the Pet Passport as you need at least a month between the blood tests before you can travel out of the UK.
Our dog is quite old and did howl whilst in the kennel (she was a rescue dog so maybe it brought back bad memories). We also had to endure the 24 hours that she refused to take a pee until eventually, and several runs in the exercise area, nature finally won! But as soon as she was out of the kennel she was fine and travelled very well. We loved the fact that she was with us for the journey.
Flying (although very expensive) is certainly the faster option. I think you just need to ask the questions like you are and feel confident that the airline staff will look after your pet whilst it's in their care. Once you find an airline that takes pets across it might be worth googling them to see if anyone has shared there experiences. Or even talk to them direct to see what's involved.
We go back in June so are just having the headache of sorting the ferries - that's the other downside of driving as you have 2 ferries the timings don't always work out so you can end up with a lot of time to kill.
Anyway hope that's helped. Our dog has loved being here and I'm sure yours will too. Good luck.
Mims