I hate the idea of stockpiling. DH can testify. However, I am planning to have about one month of supplies in the house (fortunately, we have a loft and a garage so we can store things) , but only stuff which we use or which could replace the stuff we generally use ( UHT/long life milk). I have already started buying, not much, but regularly. For example, last week I picked up two extra jars and pesto and one big bag of pasta ( = two or three evening meals for the family of 2 adults and 2 children), this week I bought 2 jars of pickles from Tesco (£1.69 for one or 2 for £2, one went in the cupboard to be used and one in the "stash") and a bottle of oil. A few pounds here, a few pounds there every week. I am lucky I can afford to spend it, I know a lot of people don't have this possibility.
If it proves that nothing will happen and stockpiling has not been necessary, so much the better, I will still use the stuff, it won't go to waste. Also I really really hope that in the circumstances of a no-deal the disruptions will not be "that bad" as it's been predicted. And that after a few days or mostly weeks of confusion things will get back more or less to normal and "there will be stuff in the shops". Maybe not everything we have got used to, most probably at different prices (fortunately, again, I am one of the lucky ones that can afford prices going up; might need to buy less, might have to change our usual meals, but we'll manage. I am very aware we are lucky, a lot of people can't afford to do this). Anyway, in the situation of people panicking and emptying the shelves in the shops, or in the situation of supermarkets not being able to refill the shelves in time, or in the situation of people panicking and fighting for the last ... whatever, I would rather be in the position of staying in the house with my family and eat through our supplies and "ride the crazy weeks" until things calm down a bit. So, I am stockpiling a bit: jars, tins, pasta, rice, pulses, frozen veg, tea and coffee, UHT milk, squash and bottled water (THIS is something not on my regular shopping list, we are usually happy with the water from the tap, but... just in case), some basic medicine (painkillers like paracetamol and 'brufen, calpol, fortunately we don't need anything else), cat food and litter, basic toiletries, loo roll, detergent, stuff like that. We are on a good mortgage deal until 2022, one thing less to worry.