You can ask for more frequent reviews whenever you like. You just call up and make an appointment with whoever you see and, when they ask what the appointment is for, say "Diabetes review". They'll call you in for ones according to the practise guidelines, but you can go in as often as you like.
Similarly, you can tell them what you're planning to do and how. Even if they disagree with you, they'll be aware of it and log it in your notes so that it becomes part of your overall care plan moving forward.
Given that you've succeed in control achieved through diet previously, I'd just tell them that you want to give that another go, starting immediately, and that you'd like a check-up in 2 months (or however long you're comfortable with) to talk about medication, overall health and get your numbers logged again - weight, BG, etc. But, for the time being, you're going to give diet control a couple of months and will be in contact if you need anything.
Let the nurse do her thing - all the tests and blood pressure and whatnot, there might be a bit of polite smiling and nodding required - and then get on with your life