Does anyone know of a good resource for finding out the ease of
interchange between lines at London Underground interchange stations? I
happen to know, for example, that to change from the Victoria Line to
the Bakerloo line at Oxford Circus when travelling southbound is a
simple platform cross. But is there anywhere I can look up this sort of
information for all stations?

I am aware that the extendedness of blob gives a rough indication of
the interchange difficulty, but I would appreciate a pointer to any
website or publication which is a bit more thorough

Thanks!
MU