Graeme,
Give me the name of the ADI person that told you "... did ask AD and they said it would be fine..."
and I will have someone in the amplifier group educate them. If you want to build one circuit for
home use at room temperature, fine, but I would not go into production and build 1,000 a week.
Too often I have seen marginal designs in production for two or three years and then they get
a batch of parts that still meet the data sheet, but start failing.
Your schematic does not match the schematic given to you. The B section has no feedback
because the B output goes through the 4k75 resistor to the output of the A section. So the A
section clamps that node.
WRT "... Im a little concerned that the circuit supplied to me would need such high tolerance components to work,..." It could be that CMRR was not one of the design constraints, or no one thought of it, or if your signal is symetrical about ground, it might not matter. With a perfect op amp, you can go through a mathematical analysis and calculate CMR as a function of tolerance. The formula is in the article I referenced.
I don't know what your agreement was, but in general, no semiconductor company accepts system design responsibility. We can give it our best shot based on the facts we know, but the customer usually knows some small detail that we don't that can make a difference.
Harry