A fair challenge, and the answer is on the town pages but is easy to miss, so it is worth a thread.
The series behind those pages is reanalysis data: every reading is the average across a grid cell of about eleven kilometres, not a thermometer in your town. Averaging over an area that size smooths the peaks, so a record here reads a few degrees below the hottest station in the same town on the same day.
That is why those sections are headed "warmest days in this series" rather than "on record". They are not claiming to be the record. They are claiming to be the warmest day in a consistent series that goes back to 1950 and is measured the same way every year, which is the thing that makes the trend meaningful.
If you want the actual station record for your town, the Met Office is the place for it. What this site is for is the shape of the change rather than the single hottest afternoon.