Dave Arquati wrote
[...]
Prepay will work on National Rail services in the future, but not
just yet.
[...]
As for the other TOCs, the DfT's Railways Bill 2005 mentions more
control of ticketing for the Mayor; this could mean that TOCs will be

forced into some agreement over Oyster (or perhaps the DfT will help
fund the installation jointly with TfL).

An introduction of Prepay across National Rail should take place
within
two years, but obviously there's no guarantee.

SWT states (in the free mag anyway) that they only have 19 barriered
stations, so (a) I have visited most of them and (b\0 they don't have
any infrastructure installed at most stations to handle Oyster
validation.

--
Mike D