NO HOT WATER

Help! , I turned off the mains water and all valves at hot water cylinder then changed my kitchen mixer tap for a new one,
After turning back on all the above i have cold water, but when i turn the hot tap on i get nothing.
The down stairs toilet wash basin hot & cold water is all ok, upstairs bath hot & cold water ok but upstairs basin has same problem as kitchen, no hot water.
I suspect air in the pipe work but how do i clear it, all the taps in the house are mixer types...PLEASE HELP

put hand over tap spout and turn on hot and cold tap so that the mains pressure cold pushes up the hot pipe removing the airlock.

this wont work if you have check\no return valves on the hot pipe.

thanks for fast reply.
where would i find non return valves thats if any are present ?
also how long do i need to back pressure the pipe work.
I have just been told to connect the red and blue washing machine feed pipes together, sounds like a good bet will try tomorrow with fingers crossed. any more tips would be appreciated.
thanks.....