I always start our weekly meal plan with at least 2 days which are 'something on toast' or 'freezer food', usually to coincide with our busy nights as they're so quick and easy. So cheap and means extra budget can be split across the week.
Most of our meals are '2-nighters' plus lunch the next day. So this week we'll have two nights as mentioned above, two nights of leek and potato soup, two nights of cottage pie and veg.
Our favourite frugal meals are probably vegetable macaroni cheese, bulk out with lots of broccoli, tomatoes, courgette, leek etc and homemade cheese sauce and good old bangers and mash. Sausages are such a good cheap source of meat. Got some from tesco butchers recently, very good quality, 12p each!
Foods I would love to eat more of but go without because of cost - fish, especially fresh salmon, lamb, chicken breasts, nuts and seeds, avocados, blueberries, strawberries, raspberries...hmm, making myself hungry!