when you say at the base of the cistern do you mean that there is i pipe between the cistern and the pan and if so which end is leaking? if it's the top end take the lid off the cistern grab hold of the siphon(the big thing in the middle that sucks up the water and puts it down the pipe to the toilet)and get a pair of water pump pliers(couple of quid from a pound shop or similar but must be able to open to around 40mm to go around the nut that needs tightening)and tighten big nut just under the cistern or if it's the pipe that connects to the pan thats leaking then flexible seal thats around the pipe has probably come out even if it's only a tiny bit out try and push it all the way home so that it's flush(flat)to the toilet if that does'nt work a new flexible seal is a couple of quid from a plumbers shop hope this helps
ACE
April 2011