We had the same concern with our toilet in production. We are also a packaging company producing packaging intended to come into contact with food (before ranked as high gygiene site).
Explanation: production has an appart room, where there are the handwashing sinks and then two little rooms with toilet in it. As we were really novel when we started with BRC, we hired a consultant. The consultant considered that just by locking the toilets was enough. So we could keep the handwashing usable, but the toilets became non operative. (Basically, we set up different signs (out of use) and tape with "do not enter"; and explained employees that from now on it was forbidden to access those toilets and that they needed to go to the ones outside production).
When the auditor came, he thought it was a good idea, as we didn't really wanted to contruct / throw down all that part, so he accepted it as a solution for it.
We got AA grade