I basing it on the Mountsorrel Railway. I had originally planned to do the who Great Central Railway (heritage), but that seemed too time consuming for what I had available so the branch line became more appealing.
I understand what you are saying, the R2 does seem to be a rather obscure locomotive compared to the other Pecketts. The Ruston on the railway is a plain dark green with red buffer beams so if they were to do an almost bog-standard one that's the sort of thing I would imagine them doing. But thanks for your advice, I think I will go ahead and purchase the W4.