Hi. I know this sounds simple but I can't get the top of the tap off to replace or check the cartridge. I've undone a small allen nut at the rear of the tap and expected the top to come off easily, but it refuses to budge. The other tap is the same. Is there a special method to getting these off? Needless to say I've looked at online documents from the manufacturer and they don't cover this.Thank you.
Product: https://www.staxtradecentres.co.uk/prod ... er-tap.htm