I stripped mine for a repaint many years ago. You need to open up the slot on the plate where the cone shaped adjuster is. Once the the adjuster is released wind it out of threaded block in the lamp holder. There should be a spring at the arm centre pic which clips to lamp bucket. see my other post..
Hi Woody, Thanks that makes sense. What I really want to do is remove the screw from the cone shape adjuster and replace or zinc plate. This will be tricky as there is a washer permanently fixed next to the cone which I think I will have to destroy then somehow remake afterwards. I've got the springs and have in fact ordered replacements in almost the same size from ebay. Thanks for your help, Gareth