We've just moved into a rental flat with bags of "character" and would rather fix the easy stuff ourselves rather than keep bothering the estate agents. The mixer tap for the bath has a lever in the middle which should switch it to tap only when turned to the left and shower only when turned to the right. What actually happens is that left is tap plus weak shower, middle is weak shower (with no hot water coming through unless the cold tap is almost off), and right is nothing at all. Anyone know how to fix this and is it doable by someone with no plumbing knowledge?