EU Regulation 1107/2006
Article 8
Responsibility for assistance at airports
1. The managing body of an airport shall be responsible for ensuring the provision of the assistance specified in Annex I without additional charge to disabled persons and persons with reduced mobility.
2. The managing body may provide such assistance itself. Alternatively, in keeping with its responsibility, and subject always to compliance with the quality standards referred to in Article 9(1), the managing body may contract with one or more other parties for the supply of the assistance. In cooperation with airport users, through the Airport Users Committee where one exists, the managing body may enter into such a contract or contracts on its own initiative or on request, including from an air carrier, and taking into account the existing services at the airport concerned. In the event that it refuses such a request, the managing body shall provide written justification.
3. The managing body of an airport may, on a non-discriminatory basis, levy a specific charge on airport users for the purpose of funding this assistance.
4. This specific charge shall be reasonable, cost-related, transparent and established by the managing body of the airport in cooperation with airport users, through the Airport Users Committee where one exists or any other appropriate entity. It shall be shared among airport users in proportion to the total number of all passengers that each carries to and from that airport.
5. The managing body of an airport shall separate the accounts of its activities relating to the assistance provided to disabled persons and persons with reduced mobility from the accounts of its other activities, in accordance with current commercial practice.
6. The managing body of an airport shall make available to airport users, through the Airport Users Committee where one exists or any other appropriate entity, as well as to the enforcement body or bodies referred to in Article 14, an audited annual overview of charges received and expenses made in respect of the assistance provided to disabled persons and persons with reduced mobility.
Article 9
Quality standards for assistance
1. With the exception of airports whose annual traffic is less than 150 000 commercial passenger movements, the managing body shall set quality standards for the assistance specified in Annex I and determine resource requirements for meeting them, in cooperation with airport users, through the Airport Users Committee where one exists, and organisations representing disabled passengers and passengers with reduced mobility.
2. In the setting of such standards, full account shall be taken of internationally recognised policies and codes of conduct concerning facilitation of the transport of disabled persons or persons with reduced mobility, notably the ECAC Code of Good Conduct in Ground Handling for Persons with Reduced Mobility.
3. The managing body of an airport shall publish its quality standards.
4. An air carrier and the managing body of an airport may agree that, for the passengers whom that air carrier transports to and from the airport, the managing body shall provide assistance of a higher standard than the standards referred to in paragraph 1 or provide services additional to those specified in Annex I.
5. For the purpose of funding either of these, the managing body may levy a charge on the air carrier additional to that referred to in Article 8(3), which shall be transparent, cost‐related and established after consultation of the air carrier concerned.
Article 14
Enforcement body and its tasks
1. Each Member State shall designate a body or bodies responsible for the enforcement of this Regulation as regards flights departing from or arriving at airports situated in its territory. Where appropriate, this body or bodies shall take the measures necessary to ensure that the rights of disabled persons and persons with reduced mobility are respected, including compliance with the quality standards referred to in Article 9(1). The Member States shall inform the Commission of the body or bodies designated.
2. Member States shall, where appropriate, provide that the enforcement body or bodies designated under paragraph 1 shall also ensure the satisfactory implementation of Article 8, including as regards the provisions on charges with a view to avoiding unfair competition. They may also designate a specific body to that effect.
Article 15
Complaint procedure
1. A disabled person or person with reduced mobility who considers that this Regulation has been infringed may bring the matter to the attention of the managing body of the airport or to the attention of the air carrier concerned, as the case may be.
2. If the disabled person or person with reduced mobility cannot obtain satisfaction in such way, complaints may be made to any body or bodies designated under Article 14(1), or to any other competent body designated by a Member State, about an alleged infringement of this Regulation.
3. A body in one Member State which receives a complaint concerning a matter that comes under the responsibility of a designated body of another Member State shall forward the complaint to the body of that other Member State.
4. The Member States shall take measures to inform disabled persons and persons with reduced mobility of their rights under this Regulation and of the possibility of complaint to this designated body or bodies.
I believe the UK CAA is the (in)competent body.