alex_t wrote:
I wonder, is there any official way to see some closed stations like
Aldwych or destroyed ones like British Museum? (for the purpose of
non-commercial photographing by tube enthusiast ;-)

LT museum used to do occasional tours of Aldwych and Down St. but not
in recent years. Some say this is for 'security' reasons; others have
said it is due to Health & Safety considerations - these places are,
after all, dark dirty and dangerous. So I guess your options are
getting a track/tunnel maintenance job or hiring Aldwych station -
which is frequently used for filming.

British Museum has had, I believe, no access from above since the
surface-building was demolished but the platform space with white tiled
walls can still be seen from trains - this area is used for storage and
very occasionally somebody even leaves a light on.

The two best websites for photos & descriptions of all these stations
a
www.abandonedstations.org.uk
and
www.underground-history.co.uk