Brent, Jan, Chris, thanks for the appreciative comments.
Chris, the ventilator you mention, I must admit I'm not sure what is wrong with it other than that it appeared to have been simplified into something like an inverted saucer - I think it is otherwise vaguely correct in its placement and size, is it?
The most stupid thing has happened actually; I bought your Modelling Churchills book to use as reference, before this kit arrived in the post, and while a Mk III AVRE doesn't specifically feature, there is some useful content, but I also obtained the Gun Power book and ended up using that while writing the text of the review because - almost unbelievably - I have managed to lose the Modelling Churchills book... I've looked everywhere I can think of about three times, and of course the family are like the US Govt in the X-Files, denying all knowledge of ever having seen it. I expect it will turn up eventually.