There‘s a
green way from London to Paris (Newhaven-Dieppe ferry) then you can ride through the Champagne region to get to the Rhone, Southern Germany or Switzerland, which is awesome, and high chance of tailwinds 😁
But that means getting through England of course… which is not my cup of tea, as one says 🥴
Paris to Croatia: Unless you want to cross the alps, down the Rhone, turn left in Avignon, then either follow the Med coast, or EV 8 which is a bit more inland.