I was first planning to do fly Jet2 from LBA to AMS, but their flight time on sunday was way too early. And it turns out that KLM will do disconnected return flights for seemingly no extra charge. They still charge the 10-fold fare for single trips, though. Literally. A flight from LBA to AMS can be had for £40-£50 in combination with a return flight, but as a single it would cost between £400 and £500...
But now I'm flying with KLM to London City Airport. Most options went to Heathrow, but who wants to go to Heathrow? Much too far away. If I can land in the middle of the city and wave to a former BiCon venue, that seems a much better option.
It's a shame though that online checkin is only about 30 hours in advance.
Next step: book train (or so) from London to Leeds (Horsforth, actually). What's the recommended train booking site these days? nationalrail.co.uk seems to work fine, actually.