This paper (.pdf 17 pages) reports the results of a detailed analysis carried out using published UK Met Office data up to 2017. These show:

• UK temperatures rose during the 1990s and early 2000s. This rise is associated with a similar increase in near-coastal sea surface temperatures. There has been no rise in the last decade.
• Seasonal temperatures have followed a similar pattern: a rise during the 1990s, but a levelling off since.
• This sudden rise in UK land temperature is not unprecedented, with the Central Eng- land Temperature series (CET) showing a similar occurrence in the early 18th century.
• Analysis of CET shows that despite the rise in average summer temperatures, there has been no increase in the highest daily temperatures, or the frequency of extreme high temperatures, in recent years. In fact the opposite is true. Heatwaves were far more intense in 1975 and 1976, when there were thirteen days over 30◦C. By contrast, between 2007 and 2017 there have only been two such days. (Note that there was also only been one day over 30◦C in the summer of 2018). The highest daily temperature on CET was 33.2◦C, set in 1976 and equalled in 1990.
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