Ok, so mangoes don't exactly fall into the ready-made food category but they are certainly pretty instant in eating terms. There's only really one type of mango that I eat, and that is the Indian alphonso mango. Once you've tried this fragrant, golden mango, with it's soft, sweet, creamy flesh there is no going back to the horrible, hard, green things that lurk on supermarket shelves.
Alphonso mangoes are in season now, and should be available in any Indian grocery shop (although probably more commonplace in bigger stores in areas with large Asian populations).
Cost: Can vary; box of 12 in Greater London approximately £8.00I rate them 9/10.