Just to follow this up, now the journey planner is working again, zone
1 - 2 one-day travelcard is £5.30, and cheap day return Limehouse to
Southend is £11, total £16.30.

Zone 1 - 6 one-day travelcard is £7, and cheap day return Upminster to
Southend is £9.40, total £16.40. So it looks like, if it ever did, my
calculation doesn't work with the current fares. Not much difference
though. 10p more for free travel in zones 3 - 6.

I expect one year when working this out FCC will rise point to point fares
to make the fares the same as buying the normal ticket. I expect this will
happen when seasons go zonal in 2010, though I'm not sure what they will do
when you're outside the zones to start with?

Hopefully by then though they will have rolled out some sort of smart card
scheme which will probably be best value all round... (he says)

Cheers,
Dave