On a recent ride I noticed Hertfordshire has Hertford, Hitchin, Harpenden, Hemel Hempstead, Hatfield, plus Harlow just over the border.
On the North Downs there are Warlingham, Woldingham and Whyteleafe, Westerham and (maybe) West Wickham.
Going down the A2 out of London there are Blackheath, Blackfen, Blendon, Bexleyheath, Bexley, and nearby Barnehurst and Belvedere.
Are there any more?