It could be worthwhile reading thr NICE guidelines before talking to your GP again. Their criteria meet NICE guidelines, but I note you have had a receommendation for the Libre from another Doctor. If the other Doctor is an NHS consultant, I expect his feelings and recommendation would be in writing, after the appointment where he recoomeded the course of action.
I'm guessing your argument will go around your hypos, so be sure to make it clear if these have been recurrent in nature.
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Sometimes guidelines don't seem to make much sense.