As the London tube system will only get more complicated, maybe it is time to consider using an idea from the Paris Metro: make more of names of the terminii of each line. I think that one of the biggest problems for new users of the system is the use of compass-point directions (‘Eastbound and Westbound’) at tube stations.
Sometimes I need to change at Westminster. When I do, I see that the Jubilee platforms are labelled as being for trains going ‘Westbound’ and ‘Eastbound’. Surely from the point of view of most Londoners, certainly for those who navigate by the tube map, the Jubilee line goes north-south at that point, and the sub-surface lines east-west. The District and Circle aren’t marked as going Northbound and Southbound at Westminster (which are the directions it travels at that station).
Both the Jubilee and Bakerloo lines leave Baker Street to the east. Their platforms aren’t described as Eastbound.
Signage could look like this:

With a revised (2012) tube map looking like this:

Click to enlarge.