Just an update on the situation. I haven't driven the car since the last episode and after the snow has finally gone, I went out this afternoon to do some checks rule some stuff out.
Firstly I started the car and let it warm up, I then sprayed carb cleaner all around the base of the carb and nothing happened, same when I tried pulling/pushing the airbox to 12, 3, 6 and 9 o'clock.
Secondly I then shone a torch all over the outside of the filler neck and all seems ok, and when I shined it down from the fuel cap end, it seemed black inside and couldn't see any obvious sign of rust.
I've attached images of the filler neck and cap area:
I'm not ruling out rust in the fuel tank but was wondering whether it could be the fuel pump?