Hello Lynbrown
A belated welcome to the forum from me!
It can be tempting to look at the obviously sweet or sugary things as being *the* culprit for a raised BG level, but as others have said, as far as the body is concerned there is very little difference between sucrose (sugar) and the sugar that is very quickly available from wheat, grains, rice, bread etc.
Any carbohydrate will turn to glucose in the blood, and most forms will do so somewhere between a few minutes and a few hours. In terms of grains (eg wheat) more 'processed' they are, the quicker they act. So ground finely as flour or crushed and mashed as Weetabix are likely to hit your bloodstream very fast. There is a system of measuring how quickly carbs are absorbed called Glycaemic Index or Glycaemic Load which might help your choices, but everyone is different, so the best way to find out is just as you have done - with a BG meter.
Here are some things you could try:
Try the same breakfast but only eat either the cereal or the bread for a few days and see if that is better.
Ditch the Weetabix (all cereals are like rocket fuel for me) and switch to a bread with seeds in. Seeds are harder to break down so the seedier the bread the better (eg Burgen)
Try adding some fat and/or protein into the mix eg one slice of toast with eggs rather than all-carb breakfast. Lots of recent evidence shows that eating fat has little if any impact on cholesterol, which is arguably more affected by eating carbohydrate
Remember that you are likely to be more insulin-resistant in the mornings. You may have freer rein with carbs later in the day
Good luck with it!