Thank you for the advice and support on the thread sizes it is appreciated. The 1/8 threads are now taken care of with new 1/8 th Whitworths, it the smaller size in whithworth at 3/32 that was causing difficulties, this has now been resolved with the kind help of a fellow Mayhemer, Steamboatphil, who had some. I am really happy about this because it means the engine stays nearer original. I had been considering drilling out and re threading in a larger size, as suggested, then replacing the screws with studs - thankfully, hopefully that’s not currently going to be necessary.