I don't have any of the nice British single shots, but since the discussion has turned to American single shots, I thought I'd plug my personal favorite, the Savage model 220. No external hammer and a tang safety.
I have one in combination 16ga (with poly-choke) and separate 30-30 rifle barrel with fore-end. The frame is marked model 219 which is the rifle version. Also have a 20ga that I often carry when training bird dogs over released Bobwhites.
I like'em well enough I bought a pristene .410 with full case colors for my grandson. I figure he'll learn the safety habits with it that will transfer over to the Miroku 20ga tht's also waiting for him...Geo