//About 6m metric tonnes from the Netherlands and 5m metric tonnes from Russia. The UK doesn't produce enough diesel itself to meet the demand.//
Imaginary figures?
The Import of crude oil and natural gas liquids to the UK 2019.
Norway 19,155K Metric tonnes.
United States 11,405K Metric tonnes.
Algeria 4,325K Metric tonnes.
Russia 3,800K Metric tonnes.
Nigeria 2,777K Metric tonnes.
Saudi Arabia 1,024 Metric tonnes.
There are another 10 sources listed and down there in the pack is Netherlands on 485K Metric tonnes.
//Leading export destinations
As an exporter, the UK sold more crude oil to the Netherlands than any other country. In 2018, exports to the Benelux country reached 16.8 million metric tons. However, this figure also includes crude oil volumes meant for transshipment or in transit to other destinations, like Belgium and Germany. Norway also imported some 1.14 million metric tons of crude oil from the UK.
Production of crude oil
In 2018, the UK produced nearly 47.6 million metric tons of crude oil. This was the highest figure since 2011 and an increase of 21 percent compared to the low of 37.5 million metric tons recorded in 2014//
https://www.statista.com/statistics/381963/crude-oil-and-natural-gas-import-origin-countries-to-united-kingdom-uk/