I have fitted a new sink in the kitchen, and had to drain the hot water tank as there was no shut off valve downstairs, when I'd finished and turned the water back on I've got nothing coming out of any of the hot taps in the house, I'm assuming that this is an air lock or blockage, but don't no how to fix it any ideas??

Gas or Electric Water Heater?

The reason I ask is because many people drain their Electric Hot Water Heaters, turn them back on while filling and burn out the elements.

Is there any water coming out?

First I don't know why you drained your water heater. Now that you have I think you must have stirred up some trash that was in the bottom of the water heater and it has got into your valves or aerators