Backup way of opening the car

I need to understand if there is a fall-back way of getting into my Griff. My problem stems from the fact that when I lock/immobilise the car using the fob it is kinda hit and miss whether the car will unlock using the fob. The problem really is intermittent and isn't at all predictable. BTW HF replaced my immob and key fobs last year so I have no idea whether the problem is to do with the alarm/immob or with the central locking circuit. The end result is whenever I take the car out I really have to think twice about locking the car just in case it refuses to open. With most non-TVR cars at least there's a physical exterior lock acting as a fallback. I realise I'm asking a rather sensitive security question but It would give me a bit more peace of mind knowing if there is a last resort way for me to get into the car if the locks are stuck on locked.