Bog cleaner - what will get rid of that horrid limescale?

[dorisbonkers]

Caustic soda? Bleach, Toilet Duck?

I plan a glamorous night in.

I normally use the bottle of doom or Harpic fizzy tabs (not both together) but when I've had really bad limescale the ultimate solution is to empty the bowl (flush several times so you know it's really clean water then empty the water down the sink using a yogurt pot - the idea's much worse than the reality) and then apply either several pints of neat vinegar or Limelite gel www.limeliteinfo.co.uk/products.asp (other descaling products are available - do not combine products if you value your lungs).
Leave overnight (vinegar) or for recommended time then attack with brush - repeat if necessary, but that will really truly solve your problem.

Blue bottle Harpic is the only thing that shifts it in our hard water area. Leave over night and it comes off straightaway in the morning.