>>>some poor buggers then have to appeal against each one
The only valid grounds for appeal are laid out in the Regulations I've referred to above and, somewhat strangely, emergencies (of any kind) aren't mentioned.
Further, the power of the Department of Transport to make those Regulations is given to them under the provisions of the Transport Act 2000,which also permits the DfT to state, within those Regulations, which vehicles should be exempted from penalties. It's therefore somewhat odd that the DfT has chosen not to write an exemption for emergency service vehicles into the Regulations.