Hotpoint WF640 not filling fully of water?

We have a wf640 which only seems to fill with hlaf the water it should for a wash so some clothes come out half dry. Hotpoint will only tell me it should use about 60l for the whole cycle - it uses about 30l. I've changes the hot and cold solenoid valves, checked the inlett hose for blocks/kinks. Any ideas? Is there a sensor that measures how much water is in the drum - could this be faulty?

Any help appreciated