It is your bad luck to have caught the cusp of an increase; you might be able to get the old booking reinstated (but you cannot make any routing changes). Any new booking would be at the new higher pricing. It sounds like you are wanting to go London-CPH-MAD-SanSebastian-MAD and that is allowed under the OWE rules.
Historically BA and QF have had the highest fuel surcharges, and AA and AY the lowest; however these numbers are changing monthly these days and I don't know what the present ones are ... they are all going up.