I've been trying BLW but my son is more interested in throwing food on the floor than putting it in his mouth! Can I do a mix of purees and finger foods?

Don't worry about your son throwing his food intake as his main source of nutrients would still be from his milk. My son is throwing his food about too but as many BLW-practising mummies would advise in having patience as babies are naturally curious little beings. They would mashed it up to see what it happens, throw it about.. generally only maybe 20% gets into his mouth. They would soon gradually learn how to feed themselves. I know many would advise in spoon feeding while practising BLW as it would confuse the baby and the risk of choking would be higher, but I do spoon feed my son porridge as well and so far, everything looks good! Make sure that the BLW food is soft and mashable between gums to prevent any risk of choking.