Agree it could be bleach damage.
If it is limescale try a little acetone (Nail varnish remover) rub a little with a cloth. If this doesn't remove it then it is damaged
"Please dont tell me that a light spraying of Cillit Bang could have done this?!"
I hate to say it, but from my experience Cillit Bang is the root cause of your issue. I wouldn't recommend using it on any worktop.
