BAA or any other airport operator security procedures are based on Government security (DfT) directives. I do wonder if Government actually understand the impact these directives are having on the many people like you who wish to retain an airside ID when changing jobs from one company to another. It seems totally unnecessary to go through the whole 5 year reference process again, particularly if you switch jobs immediately. It surely must be having an impact on all companies who employ airside staff.