Try 'Collectors Aircraft Models'
They're based in the Sheraton Skyline hotel near Heathrow Airport.
Give them a ring, as not all the things they do are on the website.
They custom made a mahogany GR1 for me last year, I specified year, Squadron, tail number etc. They built it, and hand painted it and it's stunning, and accurate. (Over a foot long and plinth mounted too, sits nicely on the coffee table, to the consternation of the Mrs!)
They're not cheap (mine was £250 and took 10 weeks) but then quality never has come cheap.
Not sure about brass models, but give them a go.
I hope that helps.
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