A UK registered Aircraft is operated in accordance with the UK ANO wherever it may be in the World. The licensing requirements for that aircraft are contained in the UK ANO. Art 62(1) validates any valid ICAO licence to allow you to operate that aircraft on a private flight under conditions specified in the Article. There is no territorial limit imposed in Article 62, so you can do it anywhere in the World. Nothing to do with anyone else!
Try getting the CAA to confirm that though! Unfortunately I need it in writing from them for the syndicate I want to join (and their insurers). It would also be nice to have it for my own peace of mind when abroad...