"NHS dental services in Cumbria"

Is is true that the NHS only allows 2 missed appointments before being struck off the NHS list? Is the following standard of service for NHS dental patients typical. What are the checks and balances in this situation? I rang the dental practice. Twice I got a recorded message asking me to try later. I was ringing about my dental appointment on Monday, as I was afraid that travel conditions on a journey back from the south of England may mean that I would not get back in time. After the 'answerphone' message that would not take a message I was fearful that I might not be able to alert the practice in time. On the third succesful call I learned that 24 hours notice is in any event required for cancellation, which I can see is a desirable standard.

I raised the difficulty of being unable to leave a message and was told that it was not practicable for NHS patients and informed that the service would be different for private patients. While I recognise that it could present economic challenges for the practice to respond to many messages, the facility to leave a message without the offer of follow up seems important. I have young friends with families who have been bumped off the NHS list at that practice and elsewhere, having missed 2 appointments, none with a casual attitude professional appoinments. With the difficulty of leaving messages and rigid application of 2 fails and you are out, this seems to fall short of an acceptable standard of service.

Is this common practice? What constraints does the NHS put on dental service?