As indicated in the introduction, driving to the alps can be lower carbon than flying (but not as good as taking the train). Work out the carbon consumed on your journey by using this calculator. A fuel efficient car with lots of passengers will be much better than flying, but a less efficient car with one or two passengers can be worse than a plane!
Travelling from the north or the south-west of the UK, it can be very convenient to take an overnight ferry, from Hull to Rotterdam or Zeebrugge, or from Portsmouth to Caen or Le Havre.This makes for a relaxed get away on a Friday, and an early start on Saturday.
One possibility for touring in Spain is to take your car on the ferry to Santander or Bilbao . This can be cheaper and greener than flying.