I try to use Supagrill Cocoshell briquettes but they are getting harder to find and I don't like the idea of buying 10+ bags to have the delivered by Coals2u (used to be CSL)
See if you can find square coco briquettes imported from Indonesia in the UK.
They go by different names...over here the are called Ecobrasa but in the States it's called Charcos.