Well out is out and you will have to get used to it. Food will be dearer. I was in the uk again and came home a week ago. I was surprised at the price of food and believe this will get worse.
I have a friend who is resident in Spain and she says exactly the same thing. We go self catering in Europe every year and in Italy, France, Spain, Belgium, Germany and Croatia we have found no food prices drop of stay the same. Self catering on the continent (ie in European countries is very expensive.) It used to be cheap - we marvelled at cheap goods and wine in the supermarkets years ago. Now (and we are savvy shoppers and experienced self-caterers) it's often more expensive to supermarket shop on holiday in Europe than it is at home. We have noticed prices rising every year. Fact.
Here, I often use markets to save money, as do locals abroad. If you are blaming our exit from the EU for dearer food prices, I wonder what's going on in the EU for food prices to be rising on the continent too?