Sudden idling/running issue.

Hello, another question! Sorry!
The 11 suddenly developed this running / idling issue I'm starting to run out of ideas.
It was idling perfectly and then stalled.Since then it will not idle below 1200rpm and hunts baldly,I held it at a steady 3000 yesterday and the misfire was still there.
It's had :
New manifold gasket,
New fuel pump +filter
New plugs
New Dizzy cap
Leads are good
Fresh fuel
Compression test (all cylinders at 11 bar!)
Finally a carb rebuild which made absolutely no difference! I've rechecked & blown through the idle jet which also has a new o ring.
Also popped a new coil on as I had one.
I haven't checked the Co at idle or fuel pressure at carb, but wondered whether the Fuel pressure reg could be the culprit? £50 for a ropy looking used one seems a lot to me..
Any thoughts would be bloody brilliant!
Thanks again ��