Thanks chaps, all suggestions noted and appreciated , Hagons are just down the road in Hainault and I have used them before for my Italian bikes, I will have a word with them. Adjustables are an option but as noted by Smart51 an expensive one and will not look of the period, maybe as a last resort. I was hoping that someone had found something off another car of the period that happens to fit and have roughly the same travel and spring tension.
Keep the ideas coming please!