Hi,
If you register with coeliac uk you will also receive a book from them listing a lot of foods available in supermarkets and also well known brands that you can and cannot eat,
as for your question, well regarding you level of tolerance you can usually eat cornflakes and rice krispies for starters and for some people who can tolerate it they can eat oats but be very careful as only some people can eat oats.
Depending on if you work or are unemployed you can also get a prescription from your doctor for some goods which can work out a hell of a lot cheaper than buying some stuff. bread an rolls and some biscuits are available but then again most of the bread is like a rock and is only worth toasting really, so pop along and see your doctor or nurse in your local practice.
All I can say is good luck, I have been helping my friend who has coeliacs and i do most of his shopping as he is housebound, the good new also is that this new Eu law regarding allergy and food labelling will make it a lot easier for people with allergies as a lot of foods have to be labelled by law, there is also a lot more awareness now and a lot more products available than a few years ago.
Just remember if you are not 100% sure then dont risk eating something and undoing all the hard work, I say this as it takes upto 2 years of careful eating before the bowel and stomach settles and the coeliac starts to gain weight, but one slip up and you are back to the beginning....just be careful. ;-)