Almost all correct, "auxillary towing vehicle" they were not all Austins. designed to tow large trailer pumps of all types (coventry, dennis, harland,scammel and others). As such with a full crew and equipment they would become a complete fire fighting unit. It woould have been "NFS" national fire service originally. It should of course be grey and strangely if it went onto be with a local authority brigade appears never to have been painted red. good luck with the restoation.