Many people apparently have already started stockpiling food in preparation for a No-Deal Brexit. Apparently, most people who do this opt for tinned food and other items with a long shelf life, like sugar or flour. Many people might also put extra stuff in their freezer.
However, I do wonder this is the right approach. After all, the country is not facing a repeat of the last World War, but a break-down of certain supply chains.
In particular, the problem is not that any items will be banned from reaching the UK, but that the lorries carrying them will be stuck near Dover for a long time until a customs official has checked them. (Even if the UK decides not to check anything, France and other EU countries are legally obliged to check every lorry entering the Internal Market and the Customs Union, so any lorry doing a round trip will be inspected at least once.)
So the items that are going to become scarce are the ones that are either bulky or have a short shelf life. The former will be problematic because there will be relatively few per lorry, so if the cost of a round trip to the UK doubles because of the extra time, the cost per item will go up a lot; the latter will suffer because the risk that the product goes off before it reaches the consumer gets higher, which again will increase the price or reduce the demand.
Furthermore, unless the government intervenes, we’re probably going to get higher prices rather than empty shelves. Why should the supermarkets have empty shelves if they can just double the prices instead?
So in effect I expect tomatoes and cod to double in price because they’re perishable, and toilet paper because it’s bulky.
In return, the shops will be full of cheap mackerel and herring because it won’t be worthwhile exporting them any longer.
I also wonder whether there’ll be problems with the electricity supply. As far as I know, the UK imports quite a bit of it, so it’s possible there will be power cuts. That will make it rather pointless to have stored a lot of nice food in the freezer.
If I’m right, it might be a good idea to stockpile toilet paper (80% of which is imported). However, doing the same with sugar, flour and tinned food is almost pointless. It might be better to invest in a large greenhouse (for growing lettuce and tomatoes in) and a power generator (to keep the freezer running). And prepare for your shopping bill to skyrocket!