Well, you will be pleased to know it runs (!)Not very well, but it does.
(this is not an April Fools joke by the way

)
Dropped a litre of fuel/oil mixed into the tank, just a drop in case there was a fuel leak. Seems nice and dry.
Turned switch to pos 3 but I guess first position is same for starting.
Fuel on, but the tank/carb pipe does not fill completely, but has a well of fuel, about 30mm deep then air up to the tap. I think this is not right and will not help me starting.
Choke on fully, throttle closed (so tempting to open it when starting), good shove on the kick start.
Took several kicks to get a firing stroke then nothing.
Opened the tick-over screw 1 turn from fully in (is that right?)
Added more fuel to give more head to the flow.
Repeated kicks gave nothing then one gave a short burst of running of about 3 secs.
Another few kicks and it fired smoothly, responded sharply to the twist grip (

) and ticked over/blipped for about 15 secs and died, could be sparks or I suspect fuel as it died slowly.
During this run I closed the choke to 1/2 open and it started to die, came clean when I opened the choke fully.
How long do you need to keep it choked for?
There is no air filter in place yet.
With that excitement (and some satisfaction I might add) decided to close the toys in the garage and type this!

I can see some dirt in the tank/carb pipe, so first I will change the pipe and fit the small in-line filter I have to keep the carb clean.
I welcome any suggestions to get me to the bottom line asap.
Brilliant, it sounds so nice, seems to have good throttle response, and needs a few a few tweeks to try to get it right.