The original design for Midge was by C R H Simpson and described in ME from January 1935 Volume 72 until 1937 Volume 77 by George Gentry. The Horley drawings I believe are the Dick Stockings improved version of around 1984 although I have no idea what the improvements were. Most likely in the boiler department.
This advert shows the general arrangement which might be of use to you.

By the way, we like to refer to a locomotive or an engine. A train is what is pulled or pushed by one.
Best of luck in your endeavours.
Edited By Old Elan on 22/08/2018 18:48:24
Edited By Old Elan on 22/08/2018 18:52:15