Clearly, not many of you have done your "normal" weekly shop in France for the last few years! £3.50 for a small white cabbage, in Lidl, was an eye-opener. The UK is an incredibly price-sensitive market and big retailers are as keen to maintain market share as sales. But at the moment, prices are going up for several reasons.
Supply chains are much more expensive to manage with social distancing.
We're in the "hungry gap". It happens every year when the home grown root vegetable crops run out and the leafy above ground vegetables are not fully on stream. Eating seasonal food when there's a glut brings down prices, but if you have to have x item out of season, when air freight capacity is limited, then the price will soar.
Farmers can't bring in seasonal labour from Eastern Europe to pick and pack what is growing in the numbers needed, so labour costs are up.
Buy as much as possible locally and as direct as possible. Our local butcher has farms and an abbatoir, and now takes orders over the phone. They cut and weigh and call to take payment, then you can collect. But it costs more to run this system. Nevertheless it's worth it, and prices are only a small % higher, but I bet Harrods (for whom they are the main meat supplier) has raised prices.
Between the butcher, the freezer, our local growers' distribution hub and Lidl, I almost never need to go to the supermarket for anything other than ITC pharmacy, juice, loo paper and cleaning products. Our food bill is up, but we also now have to eat every meal at home. Do not mention the wine bill; that's just embarrassing!