At the bottom/underneath your boiler you will see 2 black switches. 1 to the right and the other slightly to the left! As you can see your pressure dial is at zero! You need to increase the pressure by turning the switch to the left, this will increase the pressure and bring back your hot water. insure that you do not pass the green and go int the red on your pressure dial. Check after about 20 mins to see if the pressure dial has gone up past the green, if so bleed your radiators untill back to green. Hope this works.
Gareth Fuller
January 2009