Colm,
Titan A1 is capable of removing all the below staining, may be worth a try before a pro is called in, let me know if you need anymore information...
A1 can be used on glass, porcelain, fiberglass, metal, and tile and with no acids, its safe to use on and around all natural stones.
Here's the list of stain's A1 can help on...
Mineral Deposits
Water Spots
Acid Rain
Silica
Screen Burn
Soap Scum
Oxidation
Scale
Lime
Corrosion
Rust
Oh and welcome to the forum!
Thanks
Mike