well the top of the radiator is definately warmer, but work your way down and it gets colder, untill at the bottom where its stone cold,

so i can only guess that there is a blockage somewhere preventing the water to circulate and fill the entire radiator.

only way i can describe it is if you draw a semi circle going from bottom left, and finishing bottom right, everything above is warm, yet insdie my"imaginary" circle is cold, not very imformative i know, but i'm stumped.

I have noticed though that i can turn water off from both sides of radiator, so removing and flushing might not be a problem, i presume i can use a garden hose or something to blow it through.

My only query is though, if i'm right, a heating system is a constant flow of the same water, so, if i replace the newly flushed rad will i effectively lose some of the water from that flow, if u get what i mean,

questions questions ay, u can tell i aint a plumber, lol