My property was built in 2004. The bathroom cistern is dribbling
slightly into the bowl. That is, you flush the bowl, then if you watch
the surface in the bowl after the water has settled you can observe a
continual slight dribble that lasts indefinitely.

The mechanism looks like the most complicated device I've ever seen!
Look he
http://www.littletyke.myzen.co.uk/cistern/index.html

What is this contraption? Can anyone identify the make? I've had a
quick look in Focus DIY, but none of the replacements are similar.

On the round plastic body there is the wording "To Access Seal ---"
implying that the top part can be twisted and separated from the base
and a seal replaced.

I do have an inline shut-off in the inflow pipe, so it's easy to
isolate the cistern for repairs. To check how much water is being lost
I turned the valve off and marked the water level with a pencil line
at 13:55 this afternoon. The level is now about 2cm lower after about
one hour. That's a LOT of wastage!

Any suggestions for stopping the dribbling?

Thanks!

MM