After a 20 mile round trip yesterday i parked up in the garage, switched off and had a general nose under the bonnet. There was a buzzing-bubbling sort of noise coming from the fuel pump, this was with the engine switched off. My question is what the hell is that noise all about? The pump is under a year old too.

Air purging ???

The sound was like the pump was sucking something in like air bubbles. I assume the pump must be air tight though?

The pump should be air tight allright from the outside.
Inside there are 2 one way-valves controling the flow at each stroke.
Result is overpressure on the carb side and underpressure on the tank side.
So if there is a defect you may have petrol coming back from the overpressure area producing hissing.
Or it is a air leaking hose
Or a not properly seating float needle.

Thanks Taskos. Maybe I should replace the hoses, but the sound seemed to come from the pump. I used a length of hose from my ear to the pump to locate the sound.

The last pump did not last long either, about a year, so could well be a fault with the pump