I thought that anybody who buys tickets or tops-up online has to go to
a designated Tube Station to update their Oystercard - surely it
wouldn't be unreasonable to have to go to a Tube Station once a
week/month to collect the "refund" due from weekly/monthly price
capping ?

In the longer term if Oyster gets rolled out to National Rail one would
assume that it might become possible to nominate railway stations too, and
it will also increase the number of passengers using Oyster on the tube who
presently use paper one day travelcards because of their use of rail.

Presumably the ticket machines could be used, rather than the barriers,
so a journey wouldn't have to be made.

The problem at the moment is that the ticket machines cannot be used to
collect top-ups and you do have to make a journey. There really needs to be
readers available whose sole function is to update Oyster cards.

The functionality might not be there at the moment, but I don't see any
obvious reason why in the future nominated "Ticket Stop" shops shouldn't
also be collection points for updates.