If you check out ICAO Annex 14 Vol 1 Aerodromes and compare the TDZ markings there with the ones in CAP168 Aerodrome Licensing you can see the difference immediately.
The UK now falls under EASA for airport regulation and their preferred reference is ICAO not CAA.
Hence airports can now propose an Annex 14 solution even if that is not contained in CAP168.
I have to say well spotted D2A - ever thought of being an aerodrome inspector?