This type of data are usually collected by the the Statistics Department of the Government in each country in regular interval.
For example, I am in Canada and for us 'Statistics Canada' (a Department of the Federal Government) collect these data in regular intervals (bi-annual and annual) and make them available.
You should search what is the Government Department in UK collecting this data. Surely they should be available in easily accessible format.
I note your question was posted over a month ago, but in case it might help others I would mention a Eurostat source Food: From Farm to Fork Statistics.
This is only occasionally updated, last edition is 2011. According to the webpage, "This pocketbook provides the reader with information on how the food chain evolves in Europe; it presents a range of statistical indicators for each step of this chain from the farm to the fork, passing from production on the farm, through food processing, to logistical activities such as importing, transporting and distributing, before reaching the end consumer either through purchases made in retail outlets or through the consumption of food and drink in cafés, bars and restaurants. Its aim is to give a summary of the data currently available within Eurostat s Food: from farm to fork database."