Tedser - I am glad they finally gave you a proper diagnosis - gosh, many days I wonder what doctors do in their school that they attend for 10 years (at least here in the USA!!!!!) Anyhow - I hope that they will finally give you correct treatment and give you well deserved relief !!!! If you have infection (as you most probably have if you have puss !!!!!) it is great possibility that you have a fistula formation and than NOTHING can bring you relief but surgery . Do not be scared of any procedure if your CRS is good and with a lot of experience. Sometimes when condition is chronic (as is any condition lasting for so long), more aggressive methods give LASTING results : ))) !!!!
Best of luck with it all