In message , Tim Roll-Pickering
writes

( auto top-up)

The website says I have to nominate a station to touch in to collect on,

Not quite. It says you have to nominate a station (or tram stop) at
which "you want to activate Auto top-up" - it's a one-off process.

Once it has been activated, subsequent top-ups are triggered from any
Oyster reader, so there's no need ever to visit your nominated station
again.

but seems to imply it has to be at the start of a journey,

Yes, that's essential.

--
Paul Terry