Not my area of expertise Kirsty but have you tried contacting the 10 Sqn association for more info?. They can be contacted via their website:
I assume you already have your Grandfather-in-Law's service records?. If not, this link specifically deals with how to obtain them (+ other useful sources of info):
His service no. appears in the block 1550001 to 1575000, which I believe indicates that he enlisted in Edinburgh sometime during May 1941.