Graham Jones wrote:
Been meaning to balance my radiators for years. Gave it a go once but
messing about with fiddly thermometers did my head in. I tried a digital
one and clip on ones. Anyway while in the bath last night I came up with
a new method.

Why not by one thermometer, common or garden variety, for each radiator.
Place one thermometer on top of each radiator. Wait 15mins then do the
normal lock shield valve adjustment cycle until all thermometers read
the same.

Lidl/Aldi quite often have digital in/out thermometers at 2.99 each.
-20-70C is common.