Thanks for all the advice. And thanks for the warning - it is very seductive. I have spent a happy evening googling images of South Wales steam, and the N.C.B./industrial side is fascinat8ng. I can see me getting quite a fleet for this side, even though i only need one!
The information about the panniers is really useful, thanks. I didn’t realise they arrived on the N.C.B. as early as 1959 - so I can definitely get away with one on my early 1960s era layout. Even better I found N image of one still with its BR crests on the side, so I can use my existing one with no repainting! In the long run I will wait for a DJM austerity, but for now at least there’s someth8ng I can run