Thanks Chaps.
Dave. I did just replace the corks. I will try your suggestion to tighten the corks up a bit. However, with the fuel lines disconnected from the carb, I only get an occasional drip from the fuel pipe. I have in the past left the fuel turned on by mistake but the float has always stopped the carb from flooding. So with the fuel turned off and just the aforesaid occasional drip getting to the float chamber, the fact that overnight the carb floods seems to point to the float needle valve.
Dean. It is a 276 carb, and has tight joints with new fibre washers.
Bess. The link you gave me looked promising but is for a 376 carb and I have a 276 fitted as standard with the remote float chamber.
I guess I'd better give Draganfly a ring and see what they suggest.