am I correct in saying you would remove the yellow tabs then screw a new breaker on to the exposed connection?
Correct. Over the last few years our panels have acquired all manner of extra insulation so that just about all "hot" parts are still covered up even when the outer cover is removed. If you look in the picture just above that one I hadn't fitted the yellow covers yet, and you can just about see the lugs on the copper busbar behind the wires.
Also why no ring main circuit, I thought that was the norm for UK wiring.
Yes, the ring is pretty much accepted as the norm and you'll find it used in most new installs here (domestic and commercial), but radial circuits are equally acceptable. Our "Regs." have included certain standard radial circuit arrangements for a long time.
Personally, I'm not a fan of the ring circuit and try to avoid it whenever possible. In this particular place -- much longer than it is wide and with the panel at one end -- radials are easier anyway, in my opinion.
Can you even buy red and black single conductors anymore?
It's mostly just whatever stock is left over now, e.g.
http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Clearance_Cable/index.html Black is still available in singles, because it's now a
phase color.
Old system:
Phase A = red
Phase B = yellow
Phase C = blue
Neutral = black
New system:
Phase A = brown
Phase B = black
Phase C = gray
Neutral = blue
Are those conductors that you pull into the conduit solid or stranded?
The 1.5 and 2.5 sizes are available in both forms. 4 sq. mm and upward is all stranded.
