From
www.ryanair.com/charter/policy.html
Ryanair will make every reasonable effort to provide assistance to all of our passengers. In the case of wheelchair passengers travelling in their own wheelchairs, Ryanair will pay for and absorb the cost of this service at all of our airports. Where passengers are not travelling in a wheelchair but request wheelchair assistance at airports, Ryanair will direct those passengers to the relevant third party wheelchair assistance provider, and if a fee is charged by that provider at that particular airport, then the individual passenger will be asked to pay for it. Ryanair will continue to lobby those few airports (currently 6* out of 56 airports served) who do not provide this service free of charge, to do so.
* Dublin, Leeds-Bradford, London Luton, London Gatwick, London Stansted and Shannon.
Why would someone who needs a wheelchair, not come to the airport in their wheelchair?