There should be a large plastic bung in the center of the boot floor. Remove it and you can see the sender with the send and return pipes attached. You could remove these here and try blowing through both with an air line. These are short rubber pipes that join the steel pipes through to the engine bay behind the tank.
All three sets of pipes could be blocked; tank to steel pipes, steel pipes that run under the body and the pipes in the engine bay. You should have some sort of filter along the way too, in the engine bay if you have the mechanical pump.
