Not sure those figures tell the full story though at least as far as dairy is concerned. UK exports much more milk (and more butter) than it imports, so it remains a net exporter of dairy. Imports of milk amount to a very small percentage of what we consume. We tend to import more cheese than we produce, it's all those brie paninis to blame. Imports have increased, but so have exports.

Also, DEFRA figures for dairy produced in the UK indicate a slight increase in litres (milk) and tonnes (butter and cheese) rather than decrease between 2004 and 2016.