Unfortunately I don't think you will get anywhere as you did not actually buy 'duty free'. Ryanair's stance has been consistent on this since around 2009 and I guess they can't be breaking any laws or someone would have taken them to court and won by now. Good luck though - robbing gits :
RYANAIR RAGES AGAINST CRITICISM
Last week Ryanair hit back at criticism of its move by Airports Council International (ACI) Europe. In an extraordinary outburst it hit out at “false claims”, describing them as “rubbish”.
Perhaps underlining the need for the travel retail and airport industry to be careful with the semantics of ‘travel retail’ versus ‘duty free’, Ryanair pointed out that less than 5% of its 800-plus routes operate outside the European Union “and therefore the quantities of duty free purchased by Ryanair passengers is negligible”.
In a stinging but unsubstantiated tirade directed at ACI Europe, it added: “Airport shopping has never been ‘an integral part of the travel experience’. Passengers have no interest in ‘airport shopping’; they simply want to get through airport terminals and on to their aircraft with the shortest possible queuing time and inconvenience.”
Ryanair continued: “The key to guaranteeing low airport charges is not ‘airport shopping’ as the ACI claim, but rather the development of low cost, efficient terminal buildings, something that many of the ACI airports would know nothing about.”
It claimed that ACI’s members include “some of the biggest, most expensive, least efficient monopoly airports in Europe” including London Stansted and Dublin airports.
It noted: “Charges paid by airlines and passengers will cover the cost of efficient airport infrastructure, but not the over-specified and wasteful Taj Mahals so beloved by many of the ACI’s high cost, inefficient members including BAA Stansted and Dublin Airport."
The airline commented: “Ryanair’s one carry-on bag rule does not, as [ACI Director General] Olivier Jankovec falsely claims, ‘interfere with the ability of airports to sell duty free/travel value items’. As long as these items fit into the passenger’s 10kg carry-on bag, Ryanair’s rule will have no effect whatsoever on the sale of these items.”
Ryanair spokesman Stephen McNamara concluded: “Perhaps ACI Europe should remember that intra-EU duty free disappeared almost ten years ago, and it’s not coming back. At a time when many ACI members are reporting substantial traffic declines, perhaps Mr Jankovec and many of the other monopolists in the ACI should begin to focus on delivering to passengers what they really want, which is easy to access, efficient airport facilities and not over-priced goods masquerading as ‘travel value retail’.
"If Mr Jankovec and his members spent more time reducing queues at their expensive airports, then perhaps their passenger traffic would be growing, rather than falling, at present.”