Cheers Nick,
It was the 3x8kg bags. I will try out those 15 ones for comparison though. I'm using it as I write and it's fine. To be honest I expected to find it more difficult to control than briquettes but it sits pretty solid at temp and quite adjustable. Got some lamb on and looking forward to see how it tastes. Already smells way better than briquettes I was using. It lit in the chimney super fast with very little smoke.