I've decided to go with Coat d'Arms paints, for two reasons:
1) They're cheap - £1.70 per 18ml pot! Compare that with £2.25 for 12ml of GW paint! It works out at a shocking 18.75p per 1ml of GW paint... and a decent 9.4p for 1ml of Coat d'Arms!
2) They're identical to the old Games Workshop paints that I used to love. See this chart here for details.
This means that I can get more paint for a lot less money* (hurrah!) and the paints will be entirely compatible with all the ones I currently have and have used, meaning that there'll be less variation between figures. Joy! All I need to do now is navigate their tangled webpage and order some stuff.
* 10 Coat d'Arms paints (180ml) will cost me £17 before P&P. 10 GW paints (120ml) will cost me a mere £22.50 before P&P. That's an extra £5.50 for 20ml LESS paint.