Towards the end of the month I always bring out the big guns of cheap meals 
Bacon and spinach spaghetti- ingredients from asda (or anywhere tbh)...cooking bacon 60p, cherry tomatoes 69p spaghetti 20p, frozen chopped spinach £1 (enough for 3 meals) half fat creme fraixhe 90p garlic 30p (only need one clove though so it lasts well!) This meal feeds 4 of us and is lovely and fresh.
Corned beef hash- potatoes £1.19 (2.5kg), Corned beef £1.50, beans 46p (I always use basics as there's more juice in them!) Onion 9p
Fish pie- potatoes from pack above, frozen white fish fillets £1.75 (will do 2 fish pies), frozen prawns £1.85 (does loads of pies but also does prawn jackets etc), peas 69p (does loads of things!), instant cheese and parsley granules (this is a bloody good cheat) £1.20 (I buy the tubs so last forever!)
Sausage pasta- rigatoni 59p, sausages 66p (they get de-skinned and chopped so no need for decent quality imo) fresh spinach £1, onion 9p, grated carrot 10p, veg stock, white sauce homemade, tomato puree 40p, 1/4 pint red wine £1.65 (buy tiny bottle, use half drink half, everyone's a winner
) cheese on top
Tuna pasta bake- tuna £1.20 (2 tins), fussilli 59p, broccoli 39p, 2 tubs fresh 3 cheese sauce £2.50, cheese and breadcrumbs on top
I have loads more but that should do for now! I can feed us 3 (DP and ds are massive eaters) for less than £30 a week.