Heating Stuck On!

[Smowball]

We had two new radiators fitted on Friday. System drained etc etc.when he refilled it he couldn't get heating to stay on. Didn't make sense as it was fine before he arrived. After three hours of draining , filling, air locks etc he finally got it working and all radiators hot. He left and I turned wall thermostat to zero as didn't want heating coming on in morning as wasn't cold. Woke up and house is boiling. All radiators pumping out heat even tho wall thermostat is on zero. Only way to turn heat off onto manually go into timer and switch whole system off. He can't come bk tilll at least Tuesday so does anyone have any idea what's causing this??

[Smowball]

Haven't seemed to sort it myself. Guy is coming out today so I will let you know what he says xx