Hello, I took my bike out today after it had stood for a while. Filled it up with fuel and noticed fuel dripping from the airbox drain. I've removed the filter and with the engine running can't see any fuel getting into the airbox, any suggestions.

Could be a needle valve sticking and allowing excess fuel to drain back into the airbox but I would have thought it would have gone into the cylinder from that particular carb.
Starting the engine would/could have produced enough vibration to resettle the needle valve.
Make sure you turn off the fuel tap when parking up.