I finally worked out the problem and it's fixed. Basically, there is a one-way-valve in the fuel-tank's neck, where the filler-pipe connects onto. This valve was broken and restricting the flow of fuel from the pump.
Removing the valve fixed it.
Thanks to one and all for your responses and ideas. Team-work.
Removing the valve fixed it.
Thanks to one and all for your responses and ideas. Team-work.