Had fun & games trying to get a cistern to seal on a close coupled toilet.
As always I fitted a new kit; doughnut, plate, bolts, washers, wing nuts
- leaking like a sieve.
Sought the advice of my local independent plumbers merchant (LIPM).
Turns out that Ideal Standard are far from standard.
FYI;
The doughnut is larger than the usual one by about 40mm in diameter.
The plate is larger & completely flat, so instead of having a recessed slot where the head of the bolts go, the base of the cistern has a recess.
Standard close coupling kit simply won't work. LIPM had the Ideal Standard kits in stock - problem solved. The benefits of buying plumbing stuff from a specialist are obvious.
On the subject of close coupling kits, I bought one from Homobase once. Instead of fully threaded machine screws, it came with partly threaded bolts - and so couldn't be tightened up sufficiently.
When I returned it, the manager clearly had no idea what was wrong....