How about Glasgow > Hull, then ferry to Amsterdam, Amsterdam > Algarve? Good plan?
What about Glasgow to Troon or Stranraer then ferry over to Larne; cycle down the east side of Ireland to Cork. Brittany Ferries run a service* from Cork to Roscoff in Brittany; then cycle down the west coast of France, into Spain and then Portugal?
*Only sails on a Saturday (overnight sailing) and is seasonal, March to October. Cheap at 45 euros each (if you don't want a cabin). According to bikeroutetoaster the leg from Larne to Cork is just under 300 miles.
