Ever since I read in Good Housekeeping somewhere about putting Steredent tablets down the pan. Tried this out, left a while then gave a quick wipe with those flushable square cleaner things that clip on a stick - all the gungy stuff came away, a quick flush and it's gleaming. Hence my grin and feeling of achievement in the loo - I really, really, really need to get a life 
HOWEVER, there's still brown stains all round the top just underneath the bit where the clean water comes out (must be something in the water!) - tried scrubbing with aforementioned stick thingy but they are pretty tough - any suggestions for getting rid of these? Then I will take to going into my bathroom for the pure enjoyment of looking inside the pan 