Hi there. Glad to see an interest in Tannoy. For the longest time, I thought I was a rare or very dumb breed. I use the 800A's for tracking and mixing. You'll definately need a sub paired with these. Otherwise they are useless for bottom end.
One thing that struck me very odd, yet was something I always kept hidden from clients was "how" to listen to the 800A's. To me, and in the room I work in, it is very obvious in getting a correctly done, full midrange. Basically, walk away or roll the chair a couple feet from the dispersed field of imaging. Listen and you'll either hear hollow or very flat frequency imaging when in the room I work in. Sit in the middle at ear level to the main cone and you'll most likely get the full imaging and the "correct" way the midrange should sound. Keep working with the EQ and/or compression, and it should sound the same either away from or in front with ear level to the Tannoy800A.
That is my tip, and is probably a very subjective one at that. Maybe room plays a factor, I don't know. I'm not very knowledgable with acoustic science.
Otherwise, they sound great and have a wide field of imaging if you place them on their side. But they can occassionally be a bit flattering to freshly tracked material and may skew how you may mix.
Hope this helps in some way.
-John