My libre worked perfectly for ages and ages, then it stopped working. While I'm sure I'm in a minority I'd still advocate some blood glucose checks before you believe the libre results. For me, it under reads so badly that it's useless, I've read others say it over reads...
Having said that. I left the UK in 1999 when there were no rules about blood tests before driving. I can see the reasoning though I'm personally quite happy to sit on a blood sugar of 5 and wouldn't necessarily want to increase it. Having said that, a hypo when driving is about as dangerous as you can go....(Kill others plus yourself).