webber carb problems. Starting when warm

As title, got a standard 34/36 Webber carb on my cabby and it starts fine, run it around for a while and it runs well. The problem is when its left and then try to start it it takes a few turns over to start it, then its really spluttery until its reved through - then its fine again. I'v had a look under the bonnet and after its originally turned off, there seems to be a few air bubbles in the fuel return line - is this normal? or connected in any way??

Any Ideas??  :dontknow:

I assume this happens when warmed up and then the car is stopped for some time?

Does the fuel line or filter sit over or near the exhaust, if so it could be heat soak into the fuel line or filter body vapourising the fuel?