This getting uncanny Iain!!
Personally, the reason I moved away from the rubber mounts years ago, was because the MOT man kept saying there was too much rack movement. Of course it didn't help that I had 165 tyres which upped the stationary steering loads. I also noted that when both my father and me bought recon racks, for his Herald and my Vit, that the rack tube, despite being all shiny and fresh painted, had corroded slightly under the area where the bushes clamped. I suspect that this didn't help the bushes to clamp on a worn tube. Move on a few years and we all know about rubbish repro rubber parts. When I got my Vit there were different types of rack clamps fitted and one had had a diy fix using an exhaust clamp u bolt loosely fitted. The other side had a bent thread end. Before I buy, I would want to be certain that good quality poly bushes will grip tightly and thus pass the MOT!