Geoff, that's good news, the octagon is the same as on later cars, so the spanner will fit.
I will have more info this week, for anyone intrested, but note that the spanner alone will not do much work. Anyone using it will need sufficient space under the car (about 1,5m) in order to fit a long pipe on the end of the spanner, as a lot of force is needed. The other way, of course is to make a tool like Sus.28 (see Malcolm's one at the technical section, there must be a photo of mine somewhere in the forum). So it would be fine only if you have access to a car lift or pit.
Malcolm, the situation you describe is very common on 2CVs, with the interconnected suspension all weird things happen when you try to adjust it. It can sometimes happen to our cars,too, if for some reason adjustment of a wheel/side has been way out. Available from Renault at some time was some kind of scales to check the load on each wheels (that's corner weighting, exactly as done on race cars!).