To give you a clue of how useless the TFL Journey Planner was being, compare the sensible and silly routes for the journey I was making:
Sensible: Train from New Malden to Vauxhall, bus 360 from Vauxhall directly to my destination.
Silly: Train from New Malden to Clapham Junction, another train from Clapham Junction to Vauxhall (why? when the first train goes to Vauxhall anyway), a third train from Vauxhall to Queenstown Road (Battersea), walk from there to a bus stop, then any one of three random routes to a stop round the corner from where I wanted to go.
Just to add further aggravation, I didn't actually find the sensible route on the journey planner until after I was almost there.
So I took the train from New Malden to Clapham Junction and another train from Clapham Junction to Battersea Park, wandered around a bit until I found bus stop D, and then I got on a bus which I thought was going to Victoria via the place I needed to go. However, it deposited me at Vauxhall instead - meaning that I'd spent half a bloody hour and changed vehicle twice to go somewhere I'd have been in 2 minutes if I'd stayed on my original train. I panicked wildly because I had no idea how to go from Vauxhall to the place I needed to go and ended up getting the first bus to Victoria - which was packed and difficult to navigate because the Victoria Line was closed due to "a fatality" at Green Park. Eventually got across to Buckingham Palace Road, waited ages while every bus except the 44 came, then got to my destination stop 20 minutes late. Except I couldn't find the damn house. Walked up and down the road twice before finally giving up and ringing them.
Note to self: Never again attempt to save £1.50 (or whatever it is) by buying a zone 2-6 Travelcard instead of a zone 1-6 when I'm not absolutely sure where I'm going. It makes things bloody difficult if I end up at Waterloo or Victoria, and it's infuriating to have to pay £2.10 for a single to travel one bloody stop.