There are few different types of toilet fill valve. This article covers the quick fill toilet valve with an upturned cup and how to change a toilet fill valve. They are very popular in the UK. The other types of fill valve are the traditional ball valve, and the incorporated float valve. They all follow the same principle because they use a float of air to shut the valve off.
The cup type is very easy to install. Watch the video below for a guide on how to install one.
First shut off the water supply and flush the toilet. Remove all the water from the toilet cistern. Using a spanner and some grips, loosen the nut holding the water supply and remove. Remove the next nut up and remove the old valve. Install the new valve in reverse. To alter the water level in the cistern, use the thread on the upturned cup to lower or raise the cup height.