Gone and broken the petrol pipe connector on the inline filter. I was already under there, and had a new filter on the shelf, so thought it might be a good opportunity to change it. After 16 years of road crap and the likelihood it may start leaking any day soon (the area above the petrol tank is particularly susceptible to corrosion, causing fuel leaks) I tried very carefully to release the connector....... resulting in a lot of swearing and a broken fitting..... and the 3 x O-rings fell out and into separate pieces!
Thankfully it seems, I'm not the only one to have suffered at the hands of these connectors (even those with the proper tool to hand), but a quick search of this forum came to the rescue again, with particular thanks to Doctor Gollum & previous acquaintances!
http://www.ebay.co.uk/itm/250912389358?_trksid=p2060353.m2749.l2649&var=550053025262&ssPageName=STRK%3AMEBIDX%3AIT500mm of pipe will get you to the position shown. I bought a metre of the stuff not knowing how long it might need to be, as access above the differential is tight to say the least.

Some things work out well, and despite my reservations it didn't turn out to be such a bad job in the end. The solution may have come to me eventually, but the OOF saved the day again. Thank you.