The OP should check his installation instructions for the rad.
It was only about three months ago when I diagnosed a lack of much heat in a rad like that was because it was connected backwards.
But I really cannot remember just why it was so important to be connected correctly when at first sight it was symetrical. The builder was surprised too.
Tony, I have a similar one in my bathroom except mine has eight 1/2" connections (4 horizontal and 4 vertical if you can imagine, 2 at each corner). It came with a screw-in "bolt" with an allen key head which fit through any of these 8 connections and screws internally to the radiator into a (I guess) 3/8" hole to block it. Instructions say this must go in the same hole as the entry of the flow pipe/rad valve to force the water round the radiator. I imagine this cheaper eBay version simply has this blocked orifice built into the radiator with no option to change it.
The key to resolving this problem was that the flow and return got hot within a few minutes of each other. This was despite all the radiators in the house having a cold return pipe.
So despite being an amateur plumber, I started taking up the chipboard floor and as I suspected the plumber who put in the system has not put a break in between the flow and return pipes so the water was not flowing to the new radiator as it had an easier route back to the boiler.
A bit of rerouting the pipework to create a break and now we have a warm entire house for the first time in 5 years.
I'm just waiting for the gas bill to go through the roof now!
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