TIO
May I refer you to
THIS document. The following extracts from Condition 2 of NATS operating licence are particularly relevant
Condition 2: General obligation to provide Core Services and Specified Services
1. Without prejudice to the general power conferred under this Licence, the
Licensee shall make available:
(a) the Core Services so as to be capable of meeting on a continuing basis
any reasonable level of overall demand for such services;
5. Without extending the obligation as to the overall level of services to be provided under paragraph 1(a), the Licensee shall meet each request for the provision of the Core Services reasonably made by any person.
6. For the purposes of paragraph 5 above, a person shall be held to have
reasonably made a request for the relevant services where:
(a) the Licensee has been notified of, and has not rejected, a legitimate
flight plan from the commander of an aircraft or a recognised flight plan
processing centre to a bona fide flight which is required by applicable
safety requirements to submit to the instructions of a person providing
air traffic control in the relevant area;
7. In providing services under paragraph 1 the Licensee shall not unduly prefer or discriminate against any person or class of person in respect of the operation of the Licensee’s systems, after taking into account the need to maintain the most expeditious flow of air traffic as a whole without unreasonably delaying or diverting individual aircraft or such other criteria as the Licensee may apply from time to time with the approval of the CAA.
Para 7 may be your "get out clause" - but has the unit (or NERL) obtained CAA approval for it?