Finally got car ready and off to MOT station. Failed. One of the fail points was the rear suspension tie-bar. I checked the other car and they both look the same. Closer inspection reveals that all the tie bars were bent (deliberately) so that they could fit into the welded mounting points which are incorrectly positioned. On the car in question somebody must have recognised that there was a problem and had welded and extra rod to the tie-bar. MOT stated that the modification (bent and welded) had seriously weakened the tie-bar.
I have therefore redesigned the tie-bar and mounting arrangement and so far one side completed. Hopefully other side shortly then back for MOT.
Will post pictures and details once completed but in the meantime if you have problems with the rear bush where the assembly bolts into the welded mount then you can replace the bush with one for a Motorcycle swinging arm. Size is 12mm x 28mm x 40mm and they're less that £10 each on ebay.
Try http://www.ebay.co.uk/itm/Swinging-Arm-Bushs-OD-28mm-ID-12mm-L-40mm-/111376979246?hash=item19ee95d52e which will hopefully still be valid
... or http://www.ebay.co.uk/itm/Motorcycle-Swinging-Arm-Bushes-OD-28mm-ID-12mm-L-40mm-Honda-Chinese-Models-/270594126198?pt=LH_DefaultDomain_3&hash=item3f00aab176 if you want shiny ones.