Well I managed to get the jubilee clip off closest to the tank eventually.

When I say 'off', I actually mean I rotated the pipe with pipe grips. Then managed to junior hacksaw through using about a 10mm stroke!! Best part of half hour and I managed to wedge a screwdriver in and broke the fixing.

Just about got the tank off and emptied (into the girlfriends car!), pipes and openings covered, tools tidied away and car dropped just as it got dark.

The pump will have to wait for tomorrow. I hope it's easier to get the tank back in position!