Sooooo..
There am I, convinced the tension in the choke cable is causing my problem. I'm fiddling about and stroking the tank (as you do) and I realise that the handle bar risers for my clip-ons are causing the tension by pulling all the cables and wiring up another 32mm they weren't supposed to.
Went to my brilliant local hardware shop and got 4off 8x30mm stainless Allen bolts. Only took 20 minutes to remove both risers and get the bars secured back down.
What a difference!
When I started her up to go out for a ride, I had to adjust the idle because when I let the choke off, it was fully off.
Took her out for a couple of hours and hey presto, complete shite, in fact a little worse
I'm going to leave it in the garage until the appointment it has with a proper mechanic.
At least I've ruled out the choke, but as it's now slightly worse, the issue is looking like carburation.