Can I make a suggestion that you think about adding some bottled water? (I know some people have already!)
You're probably thinking "why water?" because we all take it for granted that we turn on the tap and we get fresh, clean water, but think about how it gets there.
I work in the water industry. Possible things that could go wrong in a worst case no deal scenario:
The chemicals required for the water treatment plant do not get here.
Power supply issues meaning plants and pumping stations shut down.
See also possible cyber critical infrastructure attacks.
If things are that bad and there is no food in the shops, no petrol reaching fuel stations, how are water treatment plant operators going to get to work? No operators means the plants shut down.
I think it's unlikely that the water supply will be affected, but it's not impossible, therefore I suggest everyone gets in some water. Most people suggest around 2litres per person per day. You can get bottles of spring water in the supermarkets for about 17p.
It's a lot of water to store though. Perhaps think about some water purification tablets as well. These are not very expensive.
I'veGotThree - I'll be fucking relieved if Brexit happens and all is ok! I'm currently worrying if my child is going to have access to their medication that they need to stay alive! So while you snipe away thinking you are oh so clever, just remember there are people up and down this country right now, genuinely fearful for their children's lives. 
And why the fuck would my stores be of no use?!