Hi all, I've got a 1930s cast iron bath in a hard water area and the limescale discolouration is very unsightly and unshiftable. I've heard of a treatment called 'diamond gleam' which coats the bath in situ and makes it like new - like re-enamelling, but without having to have the bath taken away. Costs about £400 so not cheap - has anyone had it done, or know anyone who has? Thanks!