Paul Terry wrote:

It's not "unavailable" unless you can't cross the road to the Oyster shop,

I've not seen that one well advertised as an Oyster stop - though admittedly
I tend to turn right straight out of the station - but also what happens out
of hours when the shop is closed?

and I've not seen any evidence in the 2010 fares tables of zone extension
tickets being "whacked up".

Well raising paper ticket prices to drive people onto Oyster has been the
standard strategy for years now so why shouldn't we expect it to be extended
here?