Keeping the food bills cheap - how I do it

This may sound like an impossible task, but, I was once a Sainsburys devotee, spending upwards of £100 a week on food - and that was back when it was me, my husband and a toddler. Fast forward to now, we're a family of 5 with a puppy in tow, and I can bring it in around £40 a week. That covers 79 meals a week (my eldest has school lunches) across 2 adults and 2 kids as well as food for our two cats and puppy.

So, how do I do it? 

• Make a list - as things run out during the week, I pop them on a list I keep stuck to the fridge. That way, I don't overbuy things because I can't quite remember.
• Supermarket hop - I'm fortunate enough to have all the budget supermarkets nearby, Lidl, Aldi and Netto. I'm also walking distance from most of the bigger supermarkets too, so I take advantage of it. I pick up the super six from Aldi, pop to Jack Fulton for short dated crisps (they don't last long with my husband around anyway!), head to the greengrocer for fruit & veg and top up other bits wherever is cheapest.
• Bulk buy deals - I don't mean the sort of deals that come up all the time, like fajita kits, crisps and the like, I mean serious reductions. Our local Waitrose reduce their fruit and veg heavily sometimes, so I buy it up while I can. A recent example is red peppers, reduced to 30p a kilo, making each pepper about 5p - I made red pepper soup and roasted pepper pasta sauce for the freezer as well as chopping and freezing some in portions for cooking at a later date.
• Check the cost per gram - my husband is guilty of choosing the cheaper option on the label without checking the weight. Pasta, rice, pulses - they are generally cheaper in larger packets, and they keep just fine. 
• Make your own treats - I try to make a batch of flapjacks and muesli every week, that way I know what we're eating and it works out cheaper too.
• Don't snub own brands - I buy a lot of porridge oats - a bag of Asda Smartprice oats are 75p a kilo, the same from Quaker is £2.18. Surely oats are oats?

What do you do to keep your food shop bill down?