QUOTE(AndyL @ Sep 19 2008, 06:50 PM)

Did you manage to find a teacher you're happy with?
In the end I went to someone who I already knew as a composer (amongst other things). I finished off G4 and did G5 through this teacher and am staying with him for G6. I've said on a different thread that one of the things I like about this teacher is that he's so knowledgeable about all sorts of other aspects of music as well as formal theory. He knows all about composers (their lives and their styles), he knows about instruments and the history of music - he's very much an all-round musician and fascinating to listen to. He helps me with all sorts of other things that I get involved with, and lets me pick his brains on things that are nothing to do with theory but go towards increasing my general knowledge about music matters. For me, he been a very good choice.
QUOTE(AndyL @ Sep 19 2008, 06:50 PM)

I think maybe the best way is just to phone around some of the names that look the best qualified and just ask them if they do teach up to grade 8 theory.
"Best qualified" - that comes back to the meaning of "best qualified" which was discussed on the other thread. My previous theory teacher was a BMus - you'd think that was a high enough qualification to teach the lower grades, but I remember being a bit taken aback at some of things which she didn't know offhand (like whether 8ve above the notes meant you played an octave higher or lower

) and now I've been going back through my old theory papers from G1-5 to familiarise myself again with everything, I can see that she's marked quite a few of my answers at G3 and G4 level as being correct when I know now that they're not. I know you shouldn't generalise on the basis of one experience, but nevertheless it has put me off BMus as a suitable qualification for teaching theory. (Apologies to BMus people out there - I know this is a generalisation and very unfair, but it's been my experience and rightly or wrongly I've been influenced by that

).
Slight digression but I've read recently that a student can get Music GCSE/A level (I forget which) without being able to read music notation

It just goes to show that qualifications at whatever level can be very misleading.
If I was looking again, I would look for a composer and a pianist because harmony is so important at the higher grades. My teacher often plays something on the piano to demonstrate, and I'm hoping now that I'm learning piano that it will make more sense to me.
The good news is, I think, that if you can find a higher-grade theory teacher, s/he is likely to be an enthusiastic theorist and not just teaching theory because students need the lower grades in order to move on.
Good luck with your search, I hope you find someone suitable