Hmm - all this time I thought I WAS using Human Friendly URLs and it turned out I wasn't. All my urls ended in default.aspx, but used the \var\value\ format instead of ?var=value format, which I thought HFU was.
It's only when I tried to install the Ifinity URL Master that it added in the urlformat="HumanFriendly" on uninstall that I realised that all this time I was only using half the solution! I can't change it now due to SEO reasons and duplicate content, but this really should be more publicised!
For the record I am going the whole hog with URL Master form Infinity - ie.
http://www.pokerdiy.com/Leagues/PokerLeagues/tabid/435/Default.aspx
will become
http://www.pokerdiy.com/find-poker-leagues