Just to get you all thinking, I spent 20 mins checking some ferry costs and distances/travel times to my place.

Obviously if you choose to go through France, you'll have accommodation costs to consider and the travel time will be as long or as short as you choose to make it.

Ferry Options (Brittany Ferries. Recliner seat except where indicated otherwise)

Portsmouth - St Malo (Fri 5th Sep) £97
Plymouth - Santander (Weds 3 Sep) £165
Plymouth - Santander (Sun 7 Sep) £142
Santander - Plymouth (Mon 15 Sep) £130
Poole - Cherbourg (Frid 5th Sep 23:45 departure) £70
Plymouth - Roscoff (Fri 5th Sep) £95 or £140 (Day/Night with cabin)

Eurotunnel

Folkestone - Calais £24 - £53

Road Distances (Most direct route, including motorways)

St Malo - Torrevieja 1000 miles/15hrs 20mins
Cherbourg - Torrevieja 1120 miles/17 hrs
Roscoff - Torrevieja 1100 miles/17 hrs
Santander - Torrevieja 600 miles/9 hours

I figure there's roughly £50 difference in fuel costs between the shortest (Santander) and longest (Cherbourg) routes.

Should be something to get you all talking, I hope ...