Hi . Not sure if i've read your post correct. Are you saying that you have porridge plus toast and then a fry up as a breakfast. If you are having sausage and potatoes or beans with your fry up , then you could be adding a lot more carbs onto your total for a meal. Try checking your bm's at 1 and 2 hr post meal. If you are getting a spike at this time , then it could be the gliclizide causing a strong stage 2 insulin response to a large carb meal, which triggers to much insulin and takes you low at about 3 to 31/2hrs.
Its what called a reactive hypo.
Gliclizide causes uncontrolled release of insulin , and is known to produce hypo's in some people. It would be well worth talking to your doctor about reducing or stopping the gliclizide for a shorty period to see what effect it has. You take quite a large dose in the evening , which could be causing lows during the night, Your body will then try to correct the low by preforming a liver dump. This could be why you are seeing a rise in your fasting levels.
If possible try reducing your carbs or spreading them out more during the day, the lower carbs will produce a smaller response and could help.
I find that I'm very intolerent of carbs in the morning, and as a result have only about 5gramme of carb for breakfast, I can tolerate far more in the afternoon, and this is when I have most of my carbs. It's a case of testing to find what gives you the best results.
Hope this helps resolve your problem. Keep testing !!!!