I definately agree with the cost of a CGM is nothing compared to the cost of hospital stays or dialasis or other costs that can be brought on by not having good control of diabetes.
I'm the same as you when it comes to medical doctors i'm a bit scared to say when i think something is wrong, do you have someone who would be willing to come with you and not take no for an answer?
i take my mum even though im 22! she definately fights for something for me.
Jopar's post will be very useful with the clinic you could change to, i know i've read on here before that some people haven't had access to the DAFNE course in their area but have successfully been able to do it somewhere else.
It's definately useful and if anyone would benefit im sure you would be at the top of the list.
I've only had diabetes for about 18 months now so i have had changes of medication apart from going from mixed insulin to the basal/bolus regime and when i insisted i wanted to swap my team was hesitant but agreed and i still stand by my decision,
but i guess thats a small comparision to the difference of wanting a CGM...
i also agree with Jopar about making a case to the comitee/board of your PCT.
If your doctor won't allow one then go to the person above until someone will sit down with you and let you tell your situation.
I really do hope you get one, i know CGM's can be very useful from what i've read and i've also seen someone on here who states in their signature that they have one but i can't remember who and i think they may pay for the equipment needed but had the monitor paid for by the NHS.
good luck and don't give up!!
Update us on how your getting along and i'm sure there's people like Jopar who can assist you really well, and i can just be here to add my little piece and say keep going!