Hi Erminia, my suggestion is to get the Alsa bus to Santander, or Bilbao, or further to San Sebastian, or even further still to Irun, where the Spanish Camino del Norte begins at the French/Spanish border. Then start walking the Norte from there. You’re a good hiker and fit, so walk until the stage where you will have to get a bus to Santander or Bilbao for your flight to London. You will then have a great excuse to go back to where you stopped, at another time in the future, to continue along the Norte, until you eventually arrive in Santiago
. You should meet lots of other walkers too, so you don’t have to be alone. I also don’t recommend walking “backwards”. It’s a lot more difficult than people think it is. If you started in Irun you may be able to walk as far as Bilbao, if you are really fit. It’s about 152kms – 6 walking days = just over 25kms per day.
Jill