If you're counting Liverpool Street for Norwich services wouldn't Newham count as well?All Greater London boroughs, except Westminster, Camden, Lambeth, Southwark, Kensington & Chelsea and the City of London too.
Have Wembley Stadium (Brent) or Finsbury Park (Islington) ever had intercity services, even just for events at Wembley or during closures at King's Cross?
I suspect their long-distance services all went before InterCity was introduced, but Northwood (Hillingdon) and Harrow-on-the-Hill had a few trains from Loughborough (I'd guess starting from Nottingham?) in 1952.