I can probably go round and round looking at various lenses and end up with the finest of them all, only for it to be let down by my own talent.
In the end I have ordered the Nokton 50 1.5 in black. I looked at online examples from it, and the reviews are also good, so I suspect it will be perfect for me. I'm sure a Leica lens in the right hands would show it up no trouble at all. I don't have those hands though.
That leaves me with some savings and a new lens with a great reputation. So, look out for some photos at some point!
Thanks all.
(oh and thank you for that link to the brochure - excellent!)