HSE does not have specific guidance for working in temperatures below 13°C.
You will likely be complying with the law if you work in accordance with British/European Standards but you can demonstrate compliance by alternative means.
As a first point of reference you are advised to refer to the British Standards listed below.
The standards listed are not an exhaustive list but provide a framework around which you can develop your risk assessment and start managing the problem. You may need to refer to other standards listed elsewhere, dependant on your operational circumstances.