Sounds like problem with inlet valve solenoids. There is one for the hot, and one for the cold. Fairly easy to replace if you are a confident DIYer- Disconnect from power, remove two screws holding top control panel on. You will see inlet valves on left hand side (the inlet hoses are attached to the valves, so you need to unscrew hoses). Two screws on rear of valves to remove grey plastic retainer, then valves pull up to remove. There is a rubber grommit on bottom of valves- retain this as some new valves do not come with this piece. New valves available from any good appliance repair shop. Call in the experts if you are in any doubt!!