I have a family of 4 (one in nappies). I have shopped around at all the major super markets and cannot ever bring our weekly grocery bill in under £100. We are all veggie although do eat fish and this cost covers 3 meals a day plus cleaning products, toiletries etc.
I don't think we eat anything particularly extravagant, maybe fish twice a week plus some prawns or salmon for lunch a couple of times a week. Rest of the time it's veggie meals mainly from scratch.
Genuinely don't know where I'm going wrong. I'm interested in what you spend and also what meals you make?