In reply to bpmclimb:
If you are travelling as a couple and using BnB, you can easily have enough luggage space (chest mounted smallish rucksack and large backpack, each?) to not need to go by car?, especially as car hire seems so cheap in Spain.
Train from Paris to Barcelona only takes 6 hrs, so not much further to other places, but unfortunately needs booking a couple of months in advance to be affordable.
For Barcelona, I calculated a return train trip at around £160, from Bristol, including coach from Bristol + Eurostar to Paris, then night train to Latour de Carol in the Pyrenees, but a local train from there to wherever adds several hours. Perhaps hire a car from somewhere near there?
I recently did a coach from Bristol to Marseille, with Megabus to London Vic + Flix coach from Vic to Marseille. The Flix coach was only about £70 return, goes on the Chunnel, does one change at Paris Bercy with a couple of hrs waiting, + from Marseille goes on to Genoa if you want Spain. London to Marseille is around 20 hrs, + with earplugs + a neck pillow you might sleep on the night stretch ok, especially if you pick the one that does the night stretch from Paris.
Any changes to your Flix coach tickets only cost about a fiver at most.
I'll be doing this again soon as loads of quality climbing in S France and warm + dry enough too in winter, Car hire not so cheap though.
Post edited at 12:48