Update:
All replaced, needed more planning and patience than I thought. One of the nuts was really tight, all the corrosion had "welded" them together and it took me 30 mins of wd40 and tapping, until it released free.
On a quick inspection of the old pump, it was the original pump, 104k, NO split pipes, actually they were quite strong and flexible. So i reckon it has to be the motor (brushes) which have worn out. Went for a quick spin after the job and, not noted any performance difference yet, but it certainly does start instantly, just like when the tank is full.
Checked the flow and return pipes the flow was weeping a tiny bit, so just tweeked them up a little more and have duck taped up the hatch for now ( one more inspection in a few days) , waiting for my rivet gun to arrive...
Glad it all worked out for ya, Canyon. saved a bob or two there.
Very satisfying job actually, happy I saved a small fortune by not letting a stealer do it.
If your thinking about doing it- i can recommend investing in a dremel tool, will make your like easy- you can make very accurate cuts and control the depth too. Btw the space between the tank and the body is about 1" clear- the only pipe which is higher up than that is the breather which is about half of that space in a small section.
I will post some pictures later- just going to read how to do that first.