Bit of a long shot but worth checking for is blocked fuel tank breathers.

If the tank breather is blocked and the fuel cap is sealing well a vacuum can form in the tank which stops fuel being drawn into the carby and actually sucks it out of the carb when you're parked up.

When the car's warm take the fuel cap off and see if you can hear a hissing sound as air is drawn into the tank.

Sometimes the breathers can be blocked by the charcoal canister or by the exhaust melting the breather line.

Pete