I saw your Mercian and noted the 160mm stem. Lovely looking frame by the way. I wasn't aware that they came any longer than 150mm!
Sorry, I can't answer your query, let alone provide any pics, but where can I source 150/ 160mm quill stems from? This would provide more options for buying shorter top-tubed frames. Like many others on here, I simply don't have enough bikes...
The other option is to get the longest reach bars you can find, to allow more reach, which is the approach I've taken recently, to make a 56cm top tube Raleigh work for me.