Tricky Dicky wrote:
I think what you are looking for is a TRV (thermostatic radiator valve).
There are a number of different valve bodies but several manufacturers use
the same types so bet take a photo of the valve body and nip down to your
local plumbers merchant with both head and photo and they should be able
to help you out.

Hive has a good pictorial guide as to the different types of body:
https://www.hivehome.com/radiator-va...e/installation

(they will also send free adapters, even if you don't 'yet' own a Hive)

Theo