Walter Briscoe wrote:
In message
of
Sun, 21 Sep 2008 15:57:13 in uk.transport.london, Mizter T
writes
[snip]
(And I'm pretty sure that Marylebone NR and Baker Street LU are tied
together as being a valid OOSI, and I think this is also the case with
regards to Fenchurch Street NR and Tower Hill LU - though annoyingly
Paddington NR and Lancaster Gate LU is not an OOSI.)

Both true. As is Euston Square and Euston but not ES and Warren Street.
I've just been through to LU customer services and got one of the more
helpful members of their staff. They will try to assemble a list of
those interchanges. If they do, I will forward here.

I would've thought a fairly good place to start would be the list of
stations that are valid for cross-London transfer for National Rail
ticketing purposes, as that'll give a vague idea.

The current list reads as follows:

Aldgate Farringdon Queens Park
Amersham Finsbury Park Richmond
Baker Street Greenwich Seven Sisters
Balham Highbury & Islington Southwark
Bank Kensington Olympia Stratford
Barking Kentish Town Tottenham Hale
Blackfriars King's Cross St. Pancras Tower Hill
Blackhorse Road Lancaster Gate Upminster
Cannon Street Lewisham Vauxhall
Charing Cross Limehouse Victoria
Ealing Broadway Liverpool Street Walthamstow Ctl
Edgware Road London Bridge Waterloo
Elephant & Castle Marylebone West Brompton
Embankment Moorgate West Ham
Euston Old Street West Hampstead
Euston Square Paddington Wimbledon

Cheers,

Barry