To use - very easy
To get (at the moment) - very hard - they are not funded in NHS and current waiting list for people to self fund is apparently 6 months +, you have to register interest on the site then they work through the list and when they get to you they send you an email inviting you to buy but I think at the moment some people have been waiting since april with no email to buy yet.
I was lucky and got one when it first launched and it has honestly completely changed my life and how I manage my diabetes, I have made other changes alongside but this has been the biggest thing and I hate going without it now (I can just about afford 2 x 14 day sensors a month but no more so I have to have a few days off every months and more if I knock a sensor off!), but there are teething issues not only with the wait list but other people have had issues with things like skin reactions or accuracy, so maybe I have just been very lucky that it has always done exactly as it claims on the website for me!