i had this and got rid of it by back flushing the hot supply...it had air locks...i put a hose from the bath cold tap onto the hot tap...and opened the hot tap and slowly the cold...
it occurred several times but i could never find out the cause..
you can of course dismantle the tap and see if the washer has collapsed or something is blocking the flow...
do you have isolation valves under the sink.
ps
check the gravity supply tank in the loft...it may not be filling due to a blocked or faulty ballcock...think that was my original problem as well.
Unless the pipe rises above the header tank this is unlikely. It's much more likely to be debris in the pipes somewhere which gets shifted by back flushing.
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