McRostie's Service No. tells me he was an Aussie. Unfortunately our Govt. isn't as forthcoming as the Australian, New Zealand and Canadian authorities. In the UK they seem to think it is some sort of state secret as to where a man trained etc. Nothing on line at all I'm afraid
If you have already tried the Personnel Management Agency at Innsworth then you have the places he trained and served.To find out the details of any Operations he flew, you will need to examine the Sqn Operations Record Book. These are held at the National Archives at Kew. The reference is Air 27/553 for 1944/45. Avisit there would be your best bet.