Don't need to look too far Clive.
I link the press release below that the BBC based their little piece on and clearly cite in it, (its an Austro/ Hungarian collusion). You'll notice that the data and even some of the PDF's are identical, albeit the BBC makes no attempt to hide their use of them. So where did the reports authors get their UK data from? The answer to that is contained on the last page..... Ofgem (exclusively) ... honestly
.... only fecking Ofgem ..... no attempt made to multi source ..... In other words, they've relied on the organisation with the single biggest vested interest in reporting the lowest price to inform their research. They don't even use Eurostat which is the standard cross comparator. They could have gone further. They could have used consumer research surveys (end user reporting), could have set up their own interogations of price comparison sites and built their own index, they could have used the DECC, that could have delved into the many pieces of academic university research or published trade association research, but no ... they used bloody Ofgem!!! and further more, they had no cross-tabs to challenge it.
Low and behold, Ofgem reported that they are doing a great job in keeping the price down - well who'd ever have thought that hey?
http://www.energypriceindex.com/wp-content/uploads/2013/12/HEPI_Press_Release_December-2013.pdf