Southern used to run a morning peak Victoria-Horsham via Sutton as a 455. It ran fast from Clapham to Sutton, as well as Dorking to Horsham. We only reached 73mph but it was a good run.
When 455s ended up on a Reading, 70mph was possible between Ascot and Sunningdale/ Sunningdale and V.Water, between Staines and Feltham, and 60mph between Richmond and Clapham.
There are a couple of peak Hampton Courts which run Waterloo-Surbiton-TD-Hampton Court, straight down the fasts but they're all retractioned now.
Not a 455 but a 456, when they ran the morning Richmond, Guildford, they did Egham to Ascot nonstop and would run at 70.