A low carb diet is often far more effective than any other medication for most Type 2 diabetics. The problem is that there is very little good advice on how to go about it.
You are obviously aware that your diet has slipped and may be responsible at least in part for your current readings.
Perhaps if you give us an idea of what you eat and drink in an average day, we can suggest low carb alternatives which would help bring your numbers down. With being on Gliclazide you will need to check your BG quite regularly when you alter your diet to make sure you don't go too low and change things gradually, but it is clear that some changes need to be made to reduce those readings!
Unfortunately many people do not understand that all carbs are broken down into glucose in the blood stream, even healthy ones from fruit in all it's forms (fresh, dried and juiced) and supposedly low GI options like porridge.
Here on the forum we recommend people use their BG meter to see which foods have the worst effects on them and reduce portion size or remove them from the menu altogether. Keeping a food diary along with BG readings before and 2 hours after each meal really helps to figure this out and tailor a diet to your tastes and body's tolerance. It can vary quite dramatically from one person to another. A slice of Low carb bread may be OK for one person but badly spike another person's BG. That person might be able to tolerate a small portion of porridge but not manage pasta, even the wholemeal variety. This is due to the composition of our gut biome (bacteria) being very individual as well as differences in metabolism, activity, weight and genetic elements.
I was completely gobsmacked at the prospect of living without bread, but it was a no go for me and now I just don't miss it but it takes some practice finding an alternative way of eating as it is such a staple of our modern life. Interestingly, the less carbs you eat, the less you want..... and I can say this as someone who was a sugar/chocolate addict and really loved my bread and spuds. I have a whole new diet now and I enjoy what I eat and sometimes one meal lasts me all day with maybe the odd snack occasionally, so I eat much less than I used to but I feel so much better for it.
Choosing the right low carb snacks is also really important and having plenty of them available to dip into whenever you feel peckish, particularly in the early days until your body adjusts, is really helpful in sticking to the diet.
If you like a drink and can moderate your consumption, then choosing a form of alcohol which will not spike your BG levels is also helpful, so a gin and slimline tonic or a glass of red or dry white wine or for me a rum and diet coke, but best to avoid the beer, cider, alcopops, sweet/medium wine and etc as they all contain carbs and limit yourself to one glass maybe just twice or thrice a week. If you know you can't adhere to that then probably best to avoid altogether.
I hope that gives you a bit of help in tackling your problem. As I said, we can suggest low carb alternative meals if you let us know the sort of things you currently eat.
Just so you know it doesn't have to be all sack cloth and ashes I had a 2 egg mushroom, onion, bacon, courgette and cheese omelette for breakfast this morning with a side salad of green leaves, a couple of small cherry tomatoes, cucumber and red pepper with a big dollop of cheese coleslaw (full fat variety) and a cup of coffee made with double cream. That will usually last me until tea time or maybe even the following breakfast. If you don't like a big breakfast, a dollop of Creamy Greek natural yoghurt with a few rasps and mixed seeds and chopped nuts works well. Low fat/calorie products are higher in carbs and unfortunately low fat is often recommended by NHS staff when eating a bit more fat and cutting the carbs is far more helpful both to weight loss and diabetes management.