UK 10 Warmest Years Mean UK Temperature (°C) (anomaly with respect to 1971-2000
Notice how they pulled a fast one there? The "bookends" for the thirty year periods against which the "anomaly" is calculated differ between the "global" and the "UK" figures. The global baseline was for 1960 through 1990, while the UK baseline was for 1970 through 2000. The explanation almost certainly has nothing to do with availability (or lack therof) of data. Maybe I missed it, but I did not see a defensible explanation for either the difference in the selected thirty year period start/end dates or the reason why thirty years was chosen as the period against which to list anomalies.
That difference shows the telltale traces of data "cherry picking", which is a common and devious method employed by people who intend to lie through selective usage of statistics. It opens up inconvenient questions such as whether using the same baseline in both tables would have resulted in the "wrong answer" being apparent in the published data, or whether a thirty year period was chosen (rather than, for example, a fifty year period or a one-hundred-year period) because some other choice of period would have made their presentation less "alarming". After all, manufacturing "alarm" was clearly the intent behind writing and publishing this article.
Bravo! You are, of course, correct.