mjbarnard wrote:
Two bolts go through the bottom of the cistern and screw into fixings
within holes in the back of the pan. They are designed to do this
without anything between the pan and cistern.

Supplied are conical black rubber washers (and metal washers on top) to
seal the holes in the bottom of the cistern. These leaked massively. So
I added thin plastic washers between the pan and cistern.


So you've got:

###### bolt head
--##-- washer
\\##// rubber cone
=====##====== cistern floor
~~##~~ plastic washer
@@@@@##@@@@@ W.C. bowl
#### Nut

Something like that?