"The reason prices are so high in the UK is that we have to import everything".
This is incorrect. We do not "import everything". In the case of food it depends how you measure it, but if you want to take a pessimistic view approximately 50% of our food is home grown. In some foodstuffs like wheat we are pretty much self sufficient. In others like fruit we import a significant amount :
https://www.gov.uk/government/statistics/united-kingdom-food-security-report-2021/united-kingdom-food-security-report-2021-theme-2-uk-food-supply-sources
"The UK currently produces about 60% of its domestic food consumption by economic value, part of which is exported. This means just under half of the actual food on plates is produced in the UK, including the majority of grains, meat, dairy, and eggs. This figure would be higher without exports. UK supply comprises domestic production excluding exports, plus imported food. The production to supply ratio, important for understanding the UK’s self-sufficiency, has remained stable over the last two decades, and for crops that can be commercially grown in the UK has been around 75%."
One of reasons we import a lot is because we want to eat a lot of food that cannot be grown here, and also we want 100% availability rather than seasonal.
As for food inflation, I think there are several factors. One is energy costs. The cost of food production is very dependent on energy. Energy is used to prepare the ground, grow the food, harvest the food, transport the food to the end user. For growing energy is used to make fertilizer. The other is situations like the war in Ukraine, which produces a lot of food. The production there is decreased and therefore there is more competition in the market for the produce. I also think Russia is a big producer of fertilizer. It's possible that people believe the inflation will decrease going forwards because they have some insight into the above (ie they believe energy prices will decrease and that will feed into food prices).