The refilling of the cistern has suddenly been reduced to a trickle.

We have very hard water and I suspect that may be causing the problem, but it hasn't been a gradual reduction.

The float sytem and the flushing work fine.

Do I need to strip the mechanism?

Mark, August 2010

Thank you

Have stripped the valve down and found a split in the cup washer.
Could that be the problem?

Mark, August 2010

Could be lime build up in the silent fill tube if it has one.
Could be lime build up in the inlet valve
Turn water feed OFF to cistern and remove the float arm open the end cap, big knurlend nut on end of the valve , [if the plastic type valve] remove washer and while at it replace it. Re-fit and turn water back on you should see/hear a good flow.
I had this problem and it was lime build up.

Bob, August 2010