I ordered an £8.50 tool from eBay for the ring. Two partly slotted vertical bars adjustable for width in slots in the top bar. Quite thick and appears to be made of hardened metal, so no worries about twisting. Drive hole in the middle, and adaptor for ½", so used the extendable wrench for the wheel nuts.
To begin with it seemed marginal for the vertical bars to fit the ring and still be within the access hole in the bodywork, but fortunately there is just over 30 degrees of turn available at one alignment.
HDI wrote: ↑01 Mar 2016, 21:35
Installing it without the special tool that fits the plastic securing ring is a struggle as the pump assembly is spring loaded, so it wants to push out as you need to push down and thread the securing ring on! Took about a dozen attempts before the thread started without jumping off ...
I was glad to come back to read this to check, as I hadn't realised during removal that it is sprung, and on replacement I was worried I was trapping or bending something inside, like maybe the float stuck against a possible baffle. But no, just these springs.
Another issue is an O ring seal. It is slightly stretched in situ on the flange on top of the tank, and might roll off the lip on the flange. Mine did when I'd already lowered the pump in. I read of someone fiddling this for ages, but I had someone hold the pump so I could use two hands for the O ring. And getting the ring on the thread was fine, unlike in the quote, with one hand on the top of the assembly, other on ring.
Ran pump twice for the few seconds on start, started and running perfect straight away.