Have you tried porridge? I have Quaker's 'Big Bowl' (other brands are available) with golden syrup flavour for my sweet tooth. It also acts as a slow release sugar.
Porridge is a bit controversial. It is a high carb food because it is made from grain but it has a reputation for being slow release. Unfortunately, that is not the case for everyone and a big bowl of porridge or even a small bowl, could spike someone's levels higher than toast and just as quickly as toast. Sadly, I am one of those people, so I steer clear of porridge now.... and bread/toast. Not sure about the Golden syrup flavour you mention either. Is that one of these sugar free flavourings that you get in squeezy bottles? It is important to be clear because it might lead to original poster to believe that regular Golden Syrup is OK, when it is probably worse than granular sugar.
A low carb breakfast would be eggs, however you like them. Personally I find them quick and easy scrambled in the microwave and nice with mushrooms and cheese and served on a slice of ham with some slices of tomato, or a large omelette which can have a whole variety of fillings and I serve it with a large side salad and cheese coleslaw .... yes salad for breakfast! Or mostly I have creamy Greek natural yoghurt with a few berries and mixed seeds and chopped nuts and a sprinkle of cinnamon.
@Suzy52 Just making a simple change like trying a different low carb breakfast could make a significant difference to your levels for the rest of the day.
To my way of thinking, adding a meal time insulin to your regime and continuing with your current diet is unlikely to be beneficial in the long run. If you can make just one small change every few weeks to form new better eating habits, that will benefit your general health, not just your diabetes management. I know it isn't easy because I was essentially a sugar addict pre-diagnosis, but I can tell you that I feel so much better now that I have kicked the habit and the majority of the time I don't even crave that sweet stuff now. I am not saying that I couldn't easily slip back to the way I was because I could, much like a recovering alcoholic.... and I had a rare wobble day last week which made me feel physically unwell for several days afterwards (and I have insulin to cover what I eat), but I am back in control again now and happy to be eating healthily again. That old way of eating was killing me and since changing to a low carb way of eating, it has improved lots of other health conditions like migraine and joint pain and reduced cholesterol and I sleep really soundly.
Getting some exercise like a walk particularly after a meal, is an extremely good suggestion by
@kit.kendal.
Hopefully you can find a way to improve your eating habits and your diabetes management, but sometimes increasing doses of insulin or adding different insulin can make things worse instead of better in the long run, if you don't address your diet because it will cause you to put on weight. Just to be clear, it isn't the insulin which causes weight gain, but the food you eat. The insulin just allows your body to store that food as fat if you don't burn it off, whereas now the glucose from that food is sitting in your blood stream. The key thing is to put less glucose into your blood stream in the first place by eating less carbs.
With you being on insulin and Gliclazide, you need to make slow sustainable changes to your diet otherwise you risk going hypo. So just take it one meal at a time and make small changes and form new healthier habits.