Now this job should be simple right? No, not for me it's driving me
potty. Any advice to solve this will be gratefully received.

The cistern is a Twyford standard close coupled cistern with a
conventional syphon fitted about a year ago.

A few days ago the overflow pipe (exits into the common waste) was found
to be wet and the carpet underneath it, damp. Diagnosis is that the
float valve was still letting water into the cistern and probably needed
a new diaphragm fitting, as adjustment of the arm didn't work.

After 3/4 days of trying to fix this, no change. Have fitted the
diaphragm in both directions (don't think there's a right or wrong way
is there?).If I adjust the float arm to shut off to avoid overflow, it
takes an age (about an hour) for the cistern to fill up to the required
level - at the beginning of the fill all is OK but before you get to
half the fill level, the flow reduces down to almost a trickle and just
about shuts off nearly an hour later.

I have cleaned and removed all lime scale from all parts of the float
valve, fitted a new flat washer behind the valve itself (this stops
water going out through the screw-on coupling that holds the valve
together), and replaced the diaphragm.

The float itself is not getting stuck and the whole thing should work
OK. But I must be missing something.

I'm heading for a breakdown with this - help!

--
Brush-Head

"The meek shall inherit the earth, but not the mineral rights"
John Paul Getty 1892 - 1976
Akuity-Focus On Solutions
http://www.akuity.co.uk