The UK fuel distribution network is worthy of a separate post, but it is very simple. Taking Buncefield (yes the one that went bang) as an example, it is connected to a pipe approx 600 dia that flows from the refineries to Heathrow and other distribution points around the country. Each distribution point is known as a tank farm as this is where fuel is stored and separated, petrol tankers arrive from Tesco, asda, esso, shell etc. and fill up, they add their special product at the time they fill the tanker (this includes the red dye that is added to agricultural diesel) Fuel, be it diesel, aviation or petrol is pumped through the single pipe and stored in one of the big silver tanks you may have noticed, when the fuel becomes a mixture of petrol and diesel, the mixed fuel goes into a different tank and left to separate and the heavier fuel pumped to its respective tank, followed by the lighter fuel, ready for the next mixed fuel that comes down the pipe. So they may pump aviation fuel down the line on Monday and Tuesday with the majority going to Heathrow then on Wednesday morning a mix of aviation and diesel fuel comes through the pipe but by lunchtime it's pure diesel, friday morning its diesel and petrol mixed then petrol in the afternoon. Hope that helps to explain the process (I worked at Buncefield before the explosion) and no, it wasn't my fault ! The company that owned the pipelines was called BPA British pipeline association and the routing is covered by the official secrets act for obvious reasons, though I believe it's route is not very secret.