House just moved to has bad limescale in toilet. I've dealt with it in the bowl ok via black harpic / white vinegar etx. It is really think (and horrible discoloured in the dark greeen/brown, yuck) around and under the rim however. You know, where the water comes from when you flush. Any tips on how to get rid of this? It's really thick - I've already tried adding harpic and then a tissue over the top to 'holds the liquid in place and do its thing, but no luck.