I read the rules yesterday, they're linked somewhere on the forum.
Your diabetes must be controlled and you can't be a danger/have things that otherwise would make it unsafe for you to drive.
You must be aware of when a hypo (low) is approaching.
You must not have had more than 1 hypo that required help from someone else to manage within the past 12 months.
And you must keep your test kit with you and it has to have a memory function - you must test before driving, and every 2 hours.
That's more or less what any sane person would do before heading out in a car anyways.
The 1-3 years is because they don't want you to suddenly become much worse without them noticing and probably also because they want to keep an eye on whether you're still fit to drive.
It's a bit of hassle, it seems, but it doesn't look impossible.