asdf wrote:

Aren't there the options to renew in advance/over the phone/online?

Yes, although with the latter two, you have to nominate a Tube/DLR
station to collect the renewal from when you touch in, so it's not
much use if you don't start your journey at one.

However, there are over 2200 Oyster Ticket Stops (newsagents etc which
sell Oyster cards) in the capital, where you can renew your ticket. I
expect most people live within walking distance of at least one.

How good are these at a) handling the discounts; and b) taking credit/debit
cards for huge sums in one go?

And the barriers warn you when your ticket is about to expire, which
helps you to remember to renew it in advance so you don't end up
having to renew it on the morning.

Yeah but one goes through the barriers so fast, especially in the peak
morning, that this often doesn't register with you. And of course someone
based at a National Rail station has a strong prospect of not having
barriers to go through when they return at the end of the day.

Yes, it's annoying that you can't buy Railcard discounted Travelcards
from Tube ticket machines, even when the ticket office is closed
(meaning you have to either pay the full price, or travel without a
ticket and hope you get treated sympathetically at your destination).

Can you get Railcard discounts on any tickets from tube stations then? The
information at them is utterly unclear.