Sorry for the late reply, my phones not working so not getting upto date messages/emails.
What gauge is the loco as it looks to be 3.1/2" gauge. but maybe even 2.1/2" which isn't so common these days. If you could post some more photos of the loco from underneath, cab view, and smokebox, (with door open), I might be able to identify it better as to the design not just the body. Although locomotive designs tend to follow the same routes they do have slight variations in their design and how boiler fittings are arranged.
The prototype is a LT&SR 79 Class locomotive I believe, there is still at least one of this class that exists. LT&SR 79 Class 4-4-2T No. 80 Thundersley - Built in 1909. On static display, and is owned by the National Railway Museum (UK).
Though saying that it could also be an LMS 2P class as the outline resembles that much more closely.
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I will speak with the curator of NRM and a few other friends and get back to you tonight and find some more detailed information for you.