Edwin, a visitor to this site, found out the hard way that there is no avoiding zone 1 fare from Gipsy Hill to Notting Hill Gate. Research on the single fare finder showed that such a fare exists from both West Norwood and Crystal Palace, the stations either side of Gipsy Hill. Frustratingly, the train from Crystal Palace has to call at Gipsy Hill on the way, so it did seem like an oversight.
After quite a wait I’ve just received an email response from the fares team confirming that the avoiding zone 1 fare will be added from the next fares change in January. Thank you TfL.