Hi pinewood,
The criteria for me getting mine on the NHS back in September/October 2019 was as follows: I had to be testing at least 8 times a day (I was testing 10–12 times so this wasn't an issue), and I had to be willing to take an online course. If I'm completely honest, I knew I was going to disagree with some of what the course said (I follow a low carbohydrate diet), so I just skipped to the end and did the quiz to get the certificate. That was pretty much it in terms of getting one prescribed.
I also had to sign a form, which contained a number of stipulations for me to continue being able to get the Libre sensors: I had to show that the Libre was improving my control (particularly helping to lower the number of hypos); I had to agree to share my reader's data with my healthcare team; I had agree to scan at least eight times a day.
To share data, I upload my details to LibreView, which is a database of my results. My healthcare team can access this directly (provided I give permission, which is one of the stipulations for having the Libre). I often spend 100% of my day 'in range' (my target levels are set at 4.0–9.9). And I test anywhere between 30 and 50 times a day, so it's been easy for me to keep my Libre.
I hope that helps!