Feels a little off topic - otherwise try looking at the Newhaven to Dieppe crossing: it's normally pretty cheap, the crossing is only 4 hours (as opposed to c. 8 hours to St Malo/Caen?) and whilst it still leaves a decent chunk of driving in France it does cut down 2-3 hours and the roads out of Dieppe are pretty quiet and fast - plus, depending where you are coming from, it's less driving on the UK side to get to Newhaven than Plymouth/Portsmouth

No idea about Avios though!