As posted over on HfP, you can also boost NatWest reward points (£10=1170 Avios) and Avios for Thoughts points (20 or 40 a survey, usually; I didn't do any for a few weeks and they gave me an additional 400 points if I completed three - so I did).

I strongly suspect hotel point conversions will work too... I converted some IHG points yesterday and will see whether they're boostable. (The agent - who was very friendly - said she hadn't converted points before, and ended up calling me back a couple of hours later once she'd found someone to show her the ropes! Apparently nobody much converts points to airline miles, but hey - I like to test these things!)