Apologies for the second post but i have a question that someone will be able to answer:

On a dedion axle - there is a panhard rod, to hold the axle central? In bump and rebound, does this cause the axle to move slightly to one side in an arc? Does this matter or is the movement so little that it doesn't make a difference? If anyone knows of any good websites i can get the answer i'd be very grateful. Many thanks.

Yes the suspension will move sideways but fortunately it doesn't really matter.

Read this :- http://www.fordcapri.co.nz/acrobat/Articles/mallocksuspension.pdf#search=%22Mumford%20Linkage%22

Thank you very much - I knew someone would know :-)

the panhard rod needs to be as longs as possible, as the longer it is the (can't think of the right work) less extreme the curve. with the suspension travel on a locost, i'd be surprised if you got as much as 5mm side to side movement.

watts linkage is better, and is what i'm doing

I suggest you take a look at the Caterham set up.It uses just top radius rods and an "A" frame for lower location and side to side restraint. It will have zero side to side movement. What I dont like about a panhard rod is that it isnt symetrical, but I dont know if it matters/ makes any difference, just looks wrong to me!!
I am thinking of fitting an "A" frame or Watts linkage to mine, its got a panhard at present