Tried them and rimmerbros. No luck but thanks.
You could also try MOTACLAN.com, though I suspect they get their parts from Xpart, same as Rimmer Bros and Brown & Gammons, so if they have no stock, no one has NEW stock.
It might be worth contacting MGF&TFBitz, they also break cars and sell secondhand parts. Hose would be a no-on, but if it is ONLY the jiggle valve you need, they might have a good secondhand item, and/or good stainless steel pipes.
Their address/link is:
https://www.mgfntfbitz.co.uk/
Hope they can help