Having skimmed the linked documents, it seems to me that Ryanair's stated policy does indeed conform with the law and the proposals of the "Consultation Draft...". The Draft talks clearly about the disabled users with their own wheelchairs, and Ryanair's published policy appears to align with the recommendations.
The difficulty arises only in regard to users who do not bring their own wheelchair but request the use of one on their transit through the airport.
It is by no means clear to me that the responsibility here lies with the airline - the authorities at 50 out of the 56 airports which Ryanair serve provide such wheelchairs free of charge. Ryanair claims to be lobbying the other 6 (presumably including Stansted) to provide this service "free".
Of ocurse, the service is not "free" - a larger population simply has to cover the cost which is hidden somewhere else. Assuming that as a society we wish to accept the cost of supporting disabled people then the only question is how and across what population do you raise the "social tax". Possibilities include National Insurance or Income tax (across all "taxpayers"), airport service charges (across all "airport users"), airline fares (across everyone using the airline), or (a ridiculous extreme) a surcharge on the passengers on a specific flight.
Since at an airport the logical way for wheelchairs to be provided is by the airport authority it would seem to me that the best place to collect this social tax would be in the airport service charge, which is essentially what the 50 (out of 56) airports are doing.