Guys - thanks for the comments. It looks like I am falling victim to the infamous 5xPs lesson in life, or worse still, a breakdown of ass-u-me (tion)
I had considered replacing the Horsa with another Halifax and the position on the canvas lends itself to this (rear right quarter lined up for departure) but I live close to High Ercall and Tilstock, both of which where WWII glider pilot training locations and in the case of High Ercall in particular, have remained undeveloped ever since. This means that the associated landscape could be an accurate depiction although not as juicy as a high profile Op as initially intended.