I have just checked return crossings on the day I am travelling, outbound 4th Aug, return 4th Sept, it cost £110.64 return to go with P&O and we get a £20 meal voucher, Calais to Porcaro where we are heading for in Brittany is 361 miles.
Portsmouth - Caen return £514, Caen to Porcaro is 147 miles so I would save 214 miles which is 6.5 gallons of fuel, over £404 more on the ferry costs
Portsmouth - Le Havre return £438, Le Havre to Porcaro is 205 miles so I would save 156 miles which is 7.57 gallons of fuel, £328 more on the ferry costs
Pool - Cherbourg return £560, Cherbourg to Porcaro is 178 miles so I would save 183 miles which is 5.4 gallons on fuel, £450 more on the ferry costs
I cannot get a crossing to St Malo so that is not in the equation
£328 which is the lowest price above the Dover - Calais route would take me over 2150 miles, the highest price would take me 2970 miles so can you explain why I 'feel' it is cheaper?
I know there are ways of getting cheaper crossings but they don't work for everyone and even with discounts it would never be cost effective for me to go any other way than the short crossings