I don't know whether you've heard of her before but Jan Fennell wrote a good book on dog behaviour.
Channel4 ran a series of 1/2 hour programs a few years ago called the Dog Listener. In these, Jan Fennell would visit the homes of dogs with problems and intuitively recognise the source of the problem in terms of pack behaviour and help the owners correct the bad behaviour. The program is somewhat irrevelant I know, but I thought I would mention it in case you'd seen it.

Her methods are based upon those employed by Monty Don the Horse Whisperer and what impressed me the most is that they are completely non-violent and she demonstrably got results. Also, she doesn't advocate castration as a matter of course (but I would guess your rescue dog has already been 'done' though).

We bought her books in the hope of understanding and correcting some unwieldy behaviour in one of our Weimaraners (AKA loveable nut cases). Although the books didn't help us address the specific problems with our dog they were still a worthwhile read and they have broadened our understanding of canine behaviour in general which can't be a bad thing. I think we really need(ed) the in-home consultation they offer.
We haven't entirely ruled out a home visit but our problems don't yet justify the expense which is something like £250 + £0.35/mile each way.

Edit: Incidentally, you are more than welcome to borrow the Jan Fennell books if that helps at all.