John,
many thanks for all your advice, including editing the original post! I'll take your advice and go for a Prince of Wales married to a B12 chassis. This will be my first ever kit so I'm excited, and apprehensive, at the same time but the Prince of Wales looks a fine loco and not too expensive so, with care and a B12 chassis I should, I hope, be able to do a reasonable job of it.
thanks again for your advice,
regards
Loyal North lancs