Hi rocketman,
I did ask a question on rmweb and had several helpful answers - as a result I've ordered a book from Amazon. Drummond Locomotives by Brian Haresnape & Peter Rowledge, used, good condition £5 with £2.75 P&P.
I also am advised there is a picture in Locomotives Illustrated 144, RAS Publishing which covers LMS and Scottish tank engines. As yet I've not found a copy of this. There is also a picture on line of the last survivor in 1947 in LMS black, I'll try and highlight the location in here later.
One of the answers was that the Dean Sidings is not as dainty as it should be and had photos of his part built brass kit. What the picture and the brass kit confirm is that the fire box area behind the saddle tank should only be at the same height as the forward smoke box. This is simply not possible with the Hornby chassis as the motor sits far too high, so the Hornby Pug is also inaccurate for this reason. Now I'm not a pedantic perfectionist (it was that which drove me out of scale aircraft modelling) so the configuration of both this resin kit and the Hornby product become acceptable to me.
I was out when the postman came, but they have my decoders at the village shop. I will now convert the chassis to DCC and make certain this is running well before I proceed much further. I have to do this if I'm going to glue the resin body to the modified Hornby chassis - no going back for any changes !!!
I'm going to remove the block of white metal from the driver and firemans feet - will drill up through a foot into the leg and insert a small length of brass pin which will be mounted into a hole drilled in the cab floor. Oh my gawd ...... I'm drifting back to my aircraft set of standards !!!!

I drilled some holes - can't say what size drills as I just pick on eyeball sizeing, and have propped/plugged pieces into place - the chimny I expect to use is too deep back to front and will need a little fettling to sit neatly on the smokebox.
The exercise has been quite easy with no problems yet, although I'm not hurrying.

Now another thing to overcome will be getting Caledonian blue paint and transfers for cab-side number plate ...... and when the book arrives will it need blue, maroon shadowed C R and the crest on the saddle tank sides ? More research needed.
Geoff T.