Evening all. The toilet flush is giving trouble (for the third time this year...). This time the button often stays pressed down so water runs endlessly into the pan. I want to replace the valve without dismantling the cistern, but I don't really want that brand. I think it's Viva, iirc from when the plumber came. I would like to simply unclip and replace it. Is there a more reliable brand that will fit its cradle?