We spend about £60 a week on average (including some, but not all alcohol) for two adults, one 3 year old and a dog - although three year old eats all her meals at nursery during the week.
We don't buy cleaning products from the supermarkets - we use dilutable industrial stuff.
About once every 2 - 3 months we stock up the freezer with meat from a wholesale butcher who also has a shop counter (excellent quality - massive chicken breasts - very cheap).
Dog eats Bakers Complete which we get in bulk (2 massive sacks for £30 from Pets at Home which lasts him 2 months or more)
We spend about £120 at the beginning of the month 'stocking up' on bulk items (I'm including the meat in this): Pasta, rice, loo rolls, washing powder etc as well as the fresh shop for that week. The next three or four weeks we spend £30 - £40 a week of fruit, veg, bread, milk and anything that we have run out of.
We still throw far too much away so could probably bring this down quite a bit - and intend to this year.
This site tells you how you can feed a family of four for £25 a week. You have to like humous though 
. It wouldn't work for us, but I intend to use it as a base and supplement it a little, and hopefully get the shop down to under £200 per month.