Hardwoods to avoid for poor burning (mostly simply high moisture
content) poplar, willow, elm, holm oak and turkey oak.

Would you consider willow a hard wood ? I agree with the high moisture content
but once dried willow burns well. IMO hawthorn and apple are best for burning
but I have had a load of oak drying out all summer and it is burning
fantastically. shame I only have 2 weeks supply left then out with saw to chop
a load of elder. By the way has any one ever burnt conker ?