The list is maintained by Trevor Harley - you are right as he is Professor of Cognitive Psychology at Dundee University.
He has put together a huge amount of material and his pages are found here: http://www.personal.dundee.ac.uk/~taharley/britweather.htm
His lists of maximum and minimum temperatures each year are here: http://www.personal.dundee.ac.uk/~taharley/hottest_and_coldest_days.htm