I have a Daryl Hydracadia corner shower column. It has 3 problems that all developed nearly at the same time. It leaks when not on "head" setting. The temp and flow knobs no longer work.they just spin freely. Our usual plumber said it's beyond him. Showerdoc say they might have parts but need me to remove cartridges or open up the column to send them pics. There seem to be no grub screws to find. Any advice about how to remove these cartridges or open up the column gratefully received.