Hi Dave! Like Mecch said, this problem is coming up more often than not...
I had my float split & sink "overnight" about a month ago. No apparent reason, just a float full of petrol. Left the float outside to evaporate, and it's still almost as full

And this was, like Mecch said a new Burlen-made Amal carb... Contact with Burlen gave me a "fake float"-poppycock tale, but I'm suspecting a manufacturing / material issue.
-Ville