I think that people are talking at cross purposes on this thread.
There is a difference between 'stocking up' and 'stockpiling' as the word has started to be used. Stocking up is having a few extra non-perishables in case you run out, or because they are cheaper to buy by the dozen, whereas stockpiling (as it is used nowadays) is more like 'panic buying', where people buy 100 loo rolls because they have heard that there is, or is going to be a shortage.
The former does not cause shortages, or impact on anyone. It's no different from having 8 jars of jam in the cupboard because you found a large box of strawberries going cheap, or making a massive Christmas cake that you are still eating at Easter - it's good housekeeping.
The latter (particularly when done to excess, such as we saw with hand sanitiser and loo rolls a few weeks ago) will cause blips in the supply chain until shops adjust their orders.
Unless there is an actual shortage of ingredients, or import issues, even that sort of buying doesn't cause long-term shortages, although having to do without essentials such as loo roll for even a day is going to be uncomfortable, and nobody needs 100 packs of the stuff.
What does happen, though, is that the shops buy far more of the basics than usual, as they know they will sell, and as they are the things that get panic bought (pasta, anyone?) so they have to make room on the shelves, and there might be a shortage of quinoa, as the space where it used to be is now taken up by pasta spirals that move faster. It looks like there is a shortage, but it is a stock control issue.
There could well be shortages after Brexit if the traffic queues at customs materialise and fruit and veg rot in the lorries. Similarly, if the Eastern European workers who used to pick soft fruit here aren't doing so, it will rot in the fields and there will be shortages in the shops.
There is little point in individuals buying large quantities though, as obviously they don't keep, so again, the shortages won't be because of stockpiling.