painting tiles

[missmoore]

I know you can buy tile paint in B&Q etc, but was wondering if this would be alright to use on tiles around a fireplace? I've recently moved into a new house with the most gorgeous marble mantlepiece, but most disgusting insert! I'm not sure if I've described myself well, but I'm wondering if the heat of the fire would affect the paint??Or even if anyone has any other ideas for hiding my disgusting insert!