Extra "hidden" charges taken from my credit car at time of car collection.

I hired a car online and paid in full. On collection at Faro Airport I was told that I couldn't have it unless I took their additional excess cover and then I was charged a "premium location surcharge" even though we returned the vehicle with a full tank of diesel. The extra charges doubled the amount I agreed to pay at the outset and the customer services team at Europcar are simply not interested - they have offered me no compensation whatsoever. Don't hire from Europcar - this type of cover is being forced on customers at the point of vehicle collection is obviously a real money-spinner for them and they are getting away with it.