Squires Gate is on the edge of the town of Blackpool (now Blackpool International Airport), and the Bothas of No.3 School of General Reconnaissance operated from here. As the Botha was designed as a General Recce and Torpedo Bomber, and was originally employed as such on North Sea patrols by 608 Sqn, it's doubtful if there was a ban on it flying over the sea.
Navigation and other training exercises were regularly mounted from the UK's west coast, across the Irish Sea to the Isle of Mann, often on a triangular course, with Jurby, to the north of the island, being a turning point or destination, and Bothas would have undertaken such exercises.
The numbers you have posted could be the serial number of the aircraft, with a typographical error, and your Uncle's Service Number. The number '61506' could be 'L6506', one of the batch from the serial range L6347 - L6546, but of course I can't be positive on this.
The National Archives at Kew hold the Squadron Operational Record Books, which show the daily movements of a particular squadron, and some of these are also available 'on-line', although I'm unsure about this regarding non-operational or training units. Whether the ORB, if found, will reveal any more than is already known is uncertain, but the Aircraft Movement Card, held at the RAF Museum, Hendon, might indicate cause of loss, or lead to further documentation, given that the serial number is correct.
Sorry I can't be of more help, but I hope this at least points you in the right direction.