Yes in the end I had to give up my goal to not buy anything more to heat my room!
I bought this ifrared stove, just 22 euros, it consumes 400W though.
Not very cheap, but is like having 4 normal lamps of 100W turned on… anyway I couldn’t work anymore here without at least 19-20°C!
This morning when I woke up I had 15°C LOL…!