If you receive poor service contact the relevant service provider. If you are not satisfied with their response contact the UK CAA who are the UK’s National Enforcement Body for Regulation (EC) 1107/2006 concerning the rights of disabled persons and persons with reduced mobility. If you flew with an operator not registered within the United Kingdom you can contact that county’s Civil Aviation Authority to find the agency responsible. The EU legislation applies to all airlines flying into Europe, and all airports within Europe.
Denied Boarding Regulation applies to all passengers travelling from within the EU and includes compensation for delays in excess of two hours.
If you are travelling to or from the US, The Air Carriers act can also apply to your flight, more information can be found from reduced mobility.
More information about your right to fly can be found in this helpful publication produced by the Equalities and Human Rights Commission.