My toilet takes about 20 minutes to fill up, I've taken the top off and had a look but can't work it out, the water comes out a hole that is so small you can hardly see it when you remove that part so the water comes out with a loud hiss.
I think newcareer means new valve, not the whole cistern.
Have you got an isolator tap in the pipework leading up to connection to the valve (just below the cistern). If so, you could easily turn off the supply, and dismantle the valve without removing it from the cistern to check for any new parts. You could also check the water pressure by turning on the isolator with the valve opened, carefully!!!!
Looks like a cheap ass siamp B&Q toilet - had exactly the same problem whilst the family were over at christmas
If you turn the water off you can unscrew the large nut next to where the fine jet of water is coming out from. Inside you should fine a rubber diaphragm with a plastic piece in the middle - this generates a pressure differential when the float drops when the toilet is flushed, which opens the valve to refill the cystern. It should have a small tear in it somewhere which is what stops it working.
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