You have effectively 11 weeks to stockpile. (Dec. will be a write off). Concentrate on buying extra tins - soups, meat, fish, fruit, veg & dried lentils, beans, pasta, rice, milk. Freeze meat, fish, veg. Water, loo rolls, aspirin, candles or lanterns, matches, batteries.

Batteries, a 1st aid kit. But concentrate on food first. Incl pet food if you have a pet. Buy a few items weekly over the next 11 weeks. I dont care if you dont have room, leave it in the hall, under a bed. Just BUY FOOD.

@BootstrapCook has a useful guide, below. And her book Tin Can Cook is useful if you dont use tinned food much. https://cookingonabootstrap.com/2018/11/15/stockpiling-for-brexit/

Oh, and water. At least a few litres. Amazon also sells water purification tablets cheaply. Extreme end, get a camping stove and lots of warm blankets, fleece. But FOOD is most important.

Seeing comments re freezes not being good as power may go off. I think power loss unlikely but if worried, cook for before freezing & if power goes out keep door shut, shld be ok for 24 hours.