There's a key underneath the boiler which can be turned to increase the water pressure - this has worked fine for years. After I last had the boiler serviced (British Gas on their cheap service deal) I noticed that the key had gone. The engineer was a bit of a bozo and I thought no more about it, assuming that a screwdriver would function just as well.
The pressure needs increasing - using a screwdriver I can turn the valve and hear water flowing but the pressure indicator stays the same. Have I been sabotaged?