hi and welcome to the forum
i guess you need to decide if you want it all gone in one go - or sold off in smaller loads.
smaller loads would be more attractive to homeowners - so a card in your local shop window would probably do the trick - because of the increase in fuel charges, people are more willing than ever to try and make savings - so if you sell it at a fair price - i'm sure you'll get quite a few inerested - that's assuming that you don't mind having people visit you at the woods.
you might meet a few really good sorts - that would take your surplus year on year.
we have quite a few private buyers that come to our woods - to collect and load their own. they save a few quid - we save time and a bit of effort.
if you want it gone in one load - try an ad on gumtree - setting out your terms and conditions ec - again i'm sure you'll get a few bites.
how long has the birch been down - as it doesn't last outside for long ?