Nah examiners ratings are for an individual. You don't have to even tell the CAA which school you intend to test at when you apply. After you have it you can work in any area of the UK. This may get the backs up of the local examiners but there is nothing they can do.
IF the examiners are listed for LPC/OPC on a A to A AOC theye can only do the LPC/OPC's for that AOC. They would have to get further approval if they wanted to do tests for another AOC.
MJ