The Super Off Peak Travelcard is only valid on weekends and bank holidays.
Only up to a point though, it's dependent on the origin.
Super Offpeak travelcards are definitely valid any day of the week on
SWT▸ 's services, but on weekdays they only become available based on the arrival time at Waterloo (usually the first train arriving after 1200). So a Super Offpeak travelcard issued from an SWT origin would also be valid on c2c's services within the zones surely?
If you were buying such a fare from SWT but with an origin in c2c's area outside the zones, then it's easy to see how a problem might arise...
As always expected, Super Offpeak causes problems because it means different things in different areas...
I just checked for a day return from Winchester to Basildon for tomorrow, and as I expected there's a Super Offpeak fare available on the 1056 departure. So from what you are saying that could cause grief from c2c staff?
Paul