Finding a proper TRV

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Hi all.

Currently my heating system has manual valves, so to be able to install Tado I need to replace all of them to thermostatic valves first.

I really want to do it on my own, but I'm having hard time to find a TRV which is compatible with both my setup and Tado.

I need male-to-male radiator-valve body which I can mount on 15mm pipe.

Upon my reseach I found that COMAP R858E is suitable with my piping system, but upon arrival I noticed that vertical installation is not possible according to it's box (see the images below).

I'm attaching some photos from my system, my old valve, and the box of the valve I tried.

Currently I installed the valve and mount Tado. It seems like working but the bottom part of the radiator stays cold. Could you please help me to figure out the problem, or find a proper valve?