Well this is what they have told me:
As per the Terms and Conditions of the promotion ‘The SPAR/VIVO European Flight Pass’ excludes compulsory charges, such as airport taxes, fuel surcharges and passenger service charges.’



Unfortunately we are unable to ascertain where your quote of £12 has originated from however this does sound like only the UK Government Departure Tax. There are other taxes that make up the airport taxes charged by an airline and Easyjet is comparable to those of AerLingus who also fly that route.



We are unable to obtain the exact taxes from Easyjet as their website does not have this facility. We therefore base our taxes on airlines that have a comparable route, such as Aer Lingus. Aer Lingus is our preferred choice of airline for this route due to their transparency of airport taxes. We offer this option to clients for this reason however Easyjet was booked for you at your request.



We hope this clarifies the situation further for you.

So basically they guessed Easyjet's taxes as a comparison with Aer Lingus.
I just wanted to know if i could prove to them that Easyjet's taxes were less and get the difference refunded.

Still waiting on Easyjet although they sent me an email to say that customer service was under severe pressure due to weather conditions in Europe and an increased number of queries!