As for the cost of missed appointments, I'm sure some of this is down to inefficient NHS admin. My dh was sent to the wrong centre for a minor procedure. By the time he got there and was told, it was too late to get to the other centre for the appt.
Also a Bil, many years after he'd moved house - and in the meantime had had several appt. letters sent to his correct address - had a letter sent to the address he'd left over 15 years previously! If the current owners hadn't forwarded it, that would have been another appt. missed.
And I've heard so many times of relatives/carers of people with dementia, repeatedly telling NHs staff that it's no use sending letters only to such patients, who will not only never remember, but will very likely hide or destroy the letters. The carer needs a copy, too.
They always quote 'patient confidentiality' but what is the use when appts. are almost certainly going to be missed? It's all very well if you have a Health and Welfare power of attorney, but some people stubbornly refuse to agree to this, esp. when dementia has in any case made them suspicious of anyone's motives.