Arriving in England via London airports Gatwick, Stanstead and Heathrow (some travel to Dublin thence across the Irish Sea) travel to Portsmouth and board the ferry to France via Dieppe or Caen or St. Malo. Ferry to Santander from Plymouth. Although Roskoff is dull it is the entrepot for Finnisterre.
Be careful cycling among lorries (HGVs) in the ports.
Cycling based in or travelling from St. Malo is ideal and there is so much promice in France. A huge country never to be fully discoved and perhaps the most civilized place to go camping and cycling occasionally or habitually staying in cheap hotels and pensions. The weather in France is so kind in the summer. Its not surprising you only see French people outside the cities and cafe workers are often locals. The French have staggeringly beautiful holiday houses. There is always an excuse to take a day off in France: No-one seems to mind.