i personally prefer the drillbit be slightly harder wood than the hearth, too hard a drill and too soft a hearth and you burn straight through, too soft a drillbit on too hard a hearth and it's like sticking a pencil in an electric sharpener, my favourite (easiest i can get to an ember) combo is willow drill and lime (linden/basswood)hearth
Cheers fella, thanks for the tip. Might struggle to find the lime, but willow should be OK. Best break out the mini tree recognition book and keep an eye out to and from work.