New Rad Valves and towel radiator . No HW, No CH.

I recently fitted a towel radiator in bathroom. Had to replace both Valves. Emptied system by removing rad downstairs and bleeding off thru valve. Fitted new valves, replaced rads. Filled up ok, bled off rads. Now no HW and no CH. Occasionaly 3 rads nearest tank get hot, most of time cold. Sounds like an airlock, but I cant get rid. No more air out of rads, no spluttering from taps. Have tried cold water pressure to move it but nothing.
Can sometimes get all to heat by shutting off hot ones one by one, but not all together. Pump is fine, but no HW return.
Any help is grateful.

read the post at the top of the forum. before we can help we need more info