I did look all round the carb, so I'd hope that I would spot a disconnected wire. But I'll have another look tonight. Thanks for the tip.
I will still head down the SU route though. It is just such a simple carb and I know it well. Should be picking one up tomorrow, so as soon as I've got the manifold elbow through, I can get on with it. Must remember to order a choke cable in too! Where is the neatest place to mount the choke on the dash? I can't see an obvious place.
Just spotted that we have an old 2" stainless steel exhaust link pipe for a Mini on the shelf...... could make the basis of a very nice snorkel :D