The part about "DfT Inspectors managed to “tailgate” pilots through the airside gate (following pilots through without being challenged)" will still happen as pilots with passes are not being asked to challenge anyone, or is the inference that we should? I'm not sure I would given the potential reaction of any serious intruder with malicious intent.
Seriously if I were of a mind to gain access to the airfield it definitely wouldn't be opportunistic as suggested or even attempted through a security gate. Anyone researching the area would find easier methods of access. In fact a determined individual with a simple readily available tool from any good hardware store can gain access to an airfield unnoticed given the length and nature of perimeter fences.
These security cards usually require a CRB check and that's for every pilot operating out of Bournemouth.
It does beg the questions; Who is paying for this and what or whom are the DfT attempting to protect the airfield from exactly?