Hey Sam,
I've been looking into this myself, just sent an email asking for information from Minimed about the costs of theirs and they said:
If you're already on the Paradigm Veo insulin pump, you "just" need the CGM starter pack which includes a 5 pack of enlite sensors, minilink (which I assume is the part which sends the results to the pump) and an enlite inserter (to insert the sensors). This costs £687. After that, the sensors cost £275 for a pack of 5, or £525 for a pack of 10 and they last around 6 days. From what I've read the Minimed ones aren't very good for lasting longer than the time stated. If you don't have an insulin pump, you'd need the Guardian too (which is basically just a standalone CGM device which your sensors link to instead of to the pump), and the cost to buy the that with the CGM starter kit is £1599 on promotion at the moment (it says it ended on 25th April but they were still running it last week).
I'd mentioned in the email that I was concerned it was out of my price range and did they have any suggestions re: funding, and if I decided to go for it did they do any sort of trial period, but they didn't offer any advice on that front unfortunately.
Having read more online, it seems the Dexcom is more popular because they're cheaper to run, the sensors last longer and I hear they're more accurate.
It seems that some people are able to get CGM funded by their local hospital, but I guess it's just a case of whether you're lucky enough to live in the right area- I can't get it at mine- but I believe it's worth asking. Apparently the best way to go about it is to weigh up the pros and cons, and if CGM could prevent serious hypos (if you have reduced awareness for example) and/or hospital admissions, and/or could save money because you're getting through a ridiculous amount of blood testing strips at present, then it's definitely worth a shot. You have to essentially present a case to them for how CGM could be the most efficient option in your case, and hope that they agree!
Also, if you're interested in trialling it out, most hospitals will allow you to loan one just for 6 days, to get a clearer picture of what's going on with your blood sugars. I'd recommend trying that before considering forking out to pay for one if that's what it comes to!
Good luck (and let us know how you get on)
Sarah