According to the UK wide data I downloaded (or my attempts with it), going from 1900 till the end of June 2023:

Our hottest month was July 2006: , 23.3C
Coldest month: January 1963: -4.5C
Wettest month: October 1903: 219.8mm rain
Driest month: February 1932: 9.6mm rain
Most sunshine: May, 2020: 266.9hrs
Least sunshine: December 1912: 19.4hrs

It looks like there is some averaging going on. I've done the Max Temp for all regions the met office supplies and I get:

UK: Jul 2006: 23.3C
England: Jul 2006: 25.2C
Wales: Aug 1995: 23.5C
Scotland: Aug 1947: 20.7C
Northern Ireland: Aug 1995: 22.1C
England and Wales: Jul 2006: 24.9C
England N: Jul 2006: 24.1C
England S: Jul 2006: 25.8C
Scotland N: Aug 1947: 20.1C
Scotland E: Jul 2006: 21.4C
Scotland W: Aug 1947: 21.6C
England E and NE: Jul 2006: 24.4C
England NW Wales N: Jul 2006: 23.3C
Midlands: Jul 2006: 25.7C
East Anglia: Jul 2006: 26.7C
England SW Wales S: Aug 1995: 24.3C
England SE Central S: Jul 2006: 26.1C Jul 2018: 26.1C

I’m pretty sure I’ll leave it at that. In the unlikely event I do have another go and get somewhere with it, I’ll start a new thread.