... Welsummer Ltd (as of October 2011).
Before then, it was owned by...
... GB Oils.
Once upon a time BoilerJuice would try to get the best price for you by aggregating quotes from people in the same area and finding the cheapest supplier. It was a brilliant idea and appeared to work quite well. When BoilerJuice was taken over by GB Oils (the largest single oil-distribution company in Great Britain), it simply claimed to "deliver millions of litres of heating oil to thousands of customers". It also claimed that "you can benefit from Group Savings as we automatically group your order with others in your area, passing any savings directly on to you", with no mention of finding the best supplier.
Now that BoilerJuice is independent once again (Welsummer Ltd is owned by Paul Ward, one of the BoilerJuice founders), it is worth keeping a close eye on them for prices. Their quote page now only offers different quotes according to how soon you want the oil delivered, but they assure us that they "offer prices from a number of participating suppliers for each postcode area we cover". They only present the cheapest price because "the supplier could change between the point of ordering and the time that the order is processed."
To read more on consolidation and oil price comparison sites, see Who are you buying your domestic heating oil from? (on Swinny.net).
Note that FuelOilDirect.co.uk is owned by GB Oils