Oh Ian,
Give the poor wee bugger a cuddle from me, cover it up and await some spring warmth, when like a pheonix, it may arise from it's slumbers.
Yesterday the Boy Bros, which inspite of a carb refurbishment, has always been a reluctant starter after being left cold for a while ( no electric fuel pump, just a microlight diaphragm replacement!) due to fuel evaporation, took its time to fire up! Clean the plugs, re-gap, then afore trying again, heat up the last plug with the MAPX blowtorch to red heat and fire it in!
Still a bit dottery, but a wee juggle of the choke and throttle got it fired up, it's a close thing between too much choke and flooding it. You'll crack the MM woes I'm sure.
Good health, Bill