<a href="http://pigyard.com/wordpress/wp-content/uploads/2020/02/cistern-repairsfeb20.jpg"><img class="alignright  wp-image-6098" src="http://pigyard.com/wordpress/wp-content/uploads/2020/02/cistern-repairsfeb20-225x300.jpg" alt="" width="186" height="248" /></a>I had noticed for a few days that water was dribbling down the back of the pan in the ensuite bathroom. After trying to clean the diaphragm between the pan and the outlet with a wipe round with my finger I came to the conclusion that the inlet valve was letting water by and as a consequence the cistern was overflowing. I bought a new inlet valve and with a little help from Nick managed to replace it and put the cistern back together. I turned the water on (no floods) and there was still a dribble. I'd solved the "wrong problem". It wasn't the inlet it was the outlet valve. After watching a brief YouTube video and examining the valve I worked out how to take it apart without removing the cistern. Behold there was a piece of mastic across the washer which I couldn't see before. After cleaning it up and putting it back together all is now well.

The lesson - don't assume what the problem is and test all possibilities first. I'm pleased to say all is working well.