Thanks Robin, that's just what I will do.
And, in my big-headed way, when I think their fix is not enough, I may well bring my demon plan B into play: namely, 1. cut removable and replacable holes in the air deflector to allow for a little more engine bay cooling and, 2, (where I think the main problem is) cut some vent holes in the plate with the prop shaft hole at the end of the gearbox cavity; with a little tweaking, this could allow air to exit at this point underneath.
I guess this is why I actually enjoy this so much: what is life without a challenge!!
CoSwoRth every penny!