Hi
@Davido Jones, welcome to the forum.
I was in a similar situation five and half years ago, albeit only about 10 kg overweight.
At that time, I was convinced that persistent weight loss is almost never achievable and all diets will fail, i.e. weight loss regimes are not sustainable. If you simply reduce calorie intake you start to lose weight, but you will always feel hungry. Even worse, after some time your base metabolic rate, BMR, will reduce and you will need fewer calories. At this point you stop losing or even start gaining weight again. You will feel hungry and miserable all the time and at some point give up and gain the weight again. There are too many people who then start again this cycle of yoyo dieting.
What convinced me to try weight loss were the books of Michael Mosley on the 5+2 diet. His method involves changing your diet and eating only 600 calories on 2 days a week. To achieve this you will not eat potatoes, pasta, rice, bread on fast days, and mainly eat vegetables, soup, an egg, or a bit of fish and chicken. However it worked, despite having a gruelling travel schedule at the time, I started losing weight and lost 10 kg in about 6 months. Intermittent fasting (IF) does not lower your BMR and has worked for many of us, i.e. we eat normally on other days, and don't feel hungry. I also started exercising and biking, which helped getting me into shape.
I have learned a lot more about nutrition since then. A major point is that carbohydrates are quick fix food. When eating chips, ice-cream or a milkshake you will feel hungry again after 2 hours. Fatty foods, like cheese, full fat yoghurt, eggs, meats on the other hand are more satiating.
Others on this forum decided to reduce carbs intake to low or very low (~20g/day) levels, compensating this with increase of fat and protein. Many reported a reduction of weight without trying.
With such a change of diet a weight loss can be sustained by many here on the forum.
So it appears to me that you are a bit ahead of yourself, but to answer your question directly, losing weight at a rate of 0.5kg up to a maximum of 1 kg a week is possible. Anything above I would consider unhealthy, effectively starving yourself continuously.
How high was your HbA1c and what medication have you been given? if you are on metformin only dieting is fine, but if you are on gluclose lowering drugs, e.g. gliclazide, you need to talk to your GP about how your diet plans will affect your medication.