(2) Presumably refunds get credited direct to the Oystercard (if I
phone customer services) so there is no need for my postal address.

Refunds (for whatever reason) are by cheque, sent to the registered
address, ditto if you ask for a printout of your last 10(?) trips.

They also now refund direct to Oyster Card but it only works if you use the
same tube station almost every day as they "send" the refund to the gates like
an online top up. When you pass through the gates you pick it up. They expire
after a week so it really has to be a station you use regularly. Lots of people
especially those using mainly the bus or with irregular travel will still have to
get refunds via cheque. Oh and you have to ask for it done this way, if you
say nothing the default is still a cheque.

The report they send you contains all the travel data they hold on you, the
last 6 weeks. I suspect this is to comply with the Data Protection Act but
someone else may know for sure.