Personal Grocery Challenge

I have noticed on a few other blogs, and other websites that there are a fair bit of personal challenges going on - decluttering, debt repaying etc, one that I like the look of (and indirectly helping in our debt repaying) is the Grocery challenge - Now as a family of 5 plus a dog we normally spend about £50 per week and this includes normal food, packed lunches, cleaning, toiletries, and pet food which I dont think is too bad? but there is always room for improvement - and so for the rest of March I am going to try and reduce this gradually by £5-£10 and then to reduce this by £10 permanently from April onwards so that our grocery shopping will be £40 per week, I have been inspired by the book title Family feasts $75 per month (I assume this is per person as it is a family of 10(I think) )which by my calculations is roughly £48 and I know I cant spend out £48 per month for a family of 5 (as much as I would love to !!) so that is the challenge and to obviously not scrimp on the quality or quantity of the food, I'll let you know how we get on.........