"Mizter T" wrote in message
...

raft of useful information snipped

Thanks for that. I'm a reasonably savvy traveller, but I totally forgot
that, of course, one would have to touch out at the last station on the
Oyster and in again at, say, East Croydon.

I'm going from Balham (where I live) to Brighton for a couple of hours-worth
of meeting and then back home. Southern's £5/£8.50 return options are
clearly the best option, rather than involving Oyster at all.

Thanks again to you and Paul.

Ian