Hi, I have a basin crosswater mixer tap that has started to leak at the handle. I've managed to take off the handle but need advice on how to remove the cartridge. According to manual is states ' using correct tool turn the nut to remove the cartridge' but there's not but just a blue holding ring ( picture attached). A friend told me to use long noise pliers but they dont seem to fit. Do I need a special type of pliers? Also this tap is now dicontinted by crosswater and doing a search for a replacement cartridge I was unable to find one , the model is Crosswater WD110DNC. Any advice would be greatly appreciated.