Do you have thermobore Dazmond?
I was working in -5.5 at 8 am this morning, and with everything on minimum, so it was 24 degrees out the boiler and Luke warm at the brush head. Steam on the glass and definitely hot enough for me.
To be safe you are supposed to go no higher then 20degress from the ambient temperature, so I did a check last thing of the day....
......it was 0.5 degrees c outside, 24 degrees out the boiler and I checked the temperature at the brush head and it was 16 degrees. That's plenty hot for me.