In reply to TheDrunkenBakers:
I clean loads of student bathrooms at this time of year as the houses become empty.
Heres what you do.
Get some thick bleach, some washing up liquid and a plastic paint kettle or bowl. Put a load of beach in, a bit of fairy and a little bit of water. Get an old paint Brush and paint it all over the area thick, and leave for 20 mins, repeat the process over and over letting the the bleach do the work. Rinse when ready. If it needs a De limescale do the same but with cilit bang bathroom after you've rinsed it. Be careful not to mix the two chemicals as it may or may not be dangerous. If it needs a bit of agitation use a washing up brush or the like. Works a treat youth