Fuel supply cock-up after filter change?

[notsofast]

Success!  I spoke to my usual garage guy and he said to fill the filter housing manually from a can, as this old diesel engine should be tolerant of any small stray dirt particles that this method might introduce.  I filled the housing to the brim, taking care to fill the 'dirty' side of the new filter, then pumped with the manual primer - and this time, I could see air bubbles moving within the pipe taking fuel from the filter housing. The bubbles seemed to keep moving backwards and forwards, so I turned on the ignition, and then when I pumped, the bubbles seemed to move along better. After a few more pumps for luck, I tried turning the key and she fired up!