"Peter Campbell Smith" wrote

Thanks for the map info. Ashford, aka Spelthorne, seems to have a
reservoir outside the M25 and Elmbridge has a few bits including the new
Downside M25 service area. So far as I can see nothing other than Epsom
and Ewell of district or unitary authority status is wholly inside.

Which London boroughs have bits outside the M25? Havering seems to, but are
there others?

Peter