Hello.
Have a read through this:
http://www.diabetes.co.uk/diet/low-carb-diabetes-diet.html
Low carbing will require less rapid acting insulin but may require adjustments (either increased or decreased) in your background insulin.
As for what can replace potatoes, wheetabix and bread - basically, nothing will come close. There are alternatives sure but they won't be anything like the original "higher carb form" purely because they'll have lower carbs. This will result ultimately in different tastes, textures, etc.
Google will help you with a million or more low carb recipes - but the secret is to set a carbohydrate limit and then allow some breads for instance, but not too much to break your limit.
So let's say you have a 100g carb limit. There's no reason why you couldn't have two slices of seeded wholemeal bread in the morning (some loaves are only 5g per slice after you deduct the fiber content). That would leave you 90g to split over your remaining 2 meals.
It's about finding what is good and manageable for you. Your dietician should be able to assist you with a target carb intake and meal plans.
Good luck,
Grant
