Why ar my radiators sooooooo hot ?

My radiators get so hot that you cant even hold your hand in front of them. I have the drayton thermostat on just below 20, the thermostat on the tank upstairs has been turned down to 40 but when the hetaing come on the radiators are boiling.

A plumber came out a few months ago to repair a leak and i asked him as one in hall was air locked. he looked at them and just agreed that they were boiling and did domething with a wrench on the one in the living room, but it didnt fix it, he also didnt sort out the air lock.

My partner fixed the airlocked radiator by switching the pump upstairs onto three and bleeding it until it got hot.

The kitchen one is now airlocked.

But im really concerned about the radiators being so hot. Sometimes i turn the thermostat down to 10 and they are still to hot, is there anything we can do ourselves to rectify the problem ?