down stairs heating not working, hot water and upstairs ok

i have a back boiler and had it and my heating serviced back in march this year. in the summer i turned all my radiators of using the individual thermostats on the radiators. when i turn my hot water on the radiators upstairs warm up regardless wether the heating is on or not.

i have now turned all the rads on again but i can not get no heat from the down stairs rads, i have tried to bleed them and had little joy.

also some of the thermostats are really tight and i have used a monkey wrench to turn them but am scared of breaking them and having water leaks.

any help or guidance would be greatly received
thanks

close upstairs and see if downstairs heat up

is pump working?

Sounds like pump has stuck and upstairs are geting warm through gravity circulation.