Upper Norwood, South London might be up there with the best, particularly a couple of microclimate locations in my garden
The main benefit lies in the unusually high sunshine totals experienced here. Anecdotal references to these from a defunct weather station in the first half of the 20th Century exactly one mile from here as the crow flies regularly cleared the totals from central London.
Personal evidence can confirm these sort of figures in Spring to early summer shower days when lines of showers from a south west direction would leave Central London with "3.5 hours of sun" in the day when the equivalent south coast has 13/14 hours. I'm always gleeful as I see this continuous stretch of cloud running across central and northern London while overhead and to the immediate south of me lies this unremitting blue sky and burning sunshine. All this thanks to the favourable distribution of hills and greenspace all around me. I don't need a Campbell-Stokes recorder to tell me my sunshine totals are more like Eastbourne than London on days like this. Similar differences occur on hot still days when the heat billows up the cloud in the city centre and I keep my blue sky six miles away.
The original weather station there had the distinction of being the'sunniest and windiest place' in the London area.