There is no restriction for the Shannon (EISN) FIR.
Coordination is not required if a standing agreement is already in place.
Coordination requests may be made for shortcuts or new routings to the
In reality due to airspace security requirements set by the UK Government it is not possible to accept coordination requests for direct routings in to the London (EGTT) or Scottish (EGPX) FIRs. Any such coordination requests should be rejected.
In the event of this taking place, once the request is rejected, you may make an outbound coordination request to the FIR boundary fix, if appropriate and if traffic permits. It is the responsibility of the controller making the coordination request to ensure suitable separation exists.