tubechallenge.com

Wembley Central also has the Overground which is still part of National Rail.

Northumberland Park, Sudbury Hill Harrow, Northolt Park, South Ruislip, West Ruislip, and the Epsom Downs branch all have 1tph.

So, overground stations count?

Course they do, they are national rail

Doesn't Knockholt only have one an hour, too?

It used to, but looks like it is 2tph now.