I dont think you can, it's a Screwfix valve but they dont seem to sell them. It's a toilet were you can't swap the valve without splitting the toilet and pan. Hence why I was hopeful I could service it.
Is this serviceable at all isn't shutting off properly? It doesn't shut of lets water over flow in to the pan. Then eventually shuts off. To swap the valve would have to split the cistern from pan as it's an ideal concealed one. Thanks