In message , Peter Frimberly
writes

I'm not totally sure where the lift connected to, but I gather it was
to the main line

Yes - more precisely, it was to the carriage sidings just north of the
Windsor lines, roughly where the taxi road to the Eurostar terminal is
now. There was originally also a second, smaller lift to take coal
wagons down to the W&C power station.

and the Bakerloo line,

No, as John wrote, there was never a Bakerloo connection. The W&C runs
below and just beyond the gate line at Waterloo, with the depot at the
east end of Lower Marsh. Then comes the Northern, further west, roughly
mid-way along most platforms. The Bakerloo is further west still, pretty
much at the country end of platforms 1-3 and so at the far easterly end
of Lower Marsh. (It then follows Westminster Bridge Road to cross the
Northern at Lambeth North.)

--
Paul Terry