I ended up with EDF as they were the existing supplier when I moved in to my rented flat 2 years ago. Thought I would stick with them as had no idea what the consumption would be, or the prices, so thought I might as well go with the flow, and they've been pretty good. Last September they sent a statement to increase our monthly DD for both gas and electricity (as all the companies were, what with the massive hike in proces generally), but a short phone call made them realise they were looking at seasonal consumption from the winter, not a whole year. And we were in credit!
They took this on board with no argument, offered to move me on to a cheaper tariff and I managed to keep my gas and leccy DDs the same in the face of big general % increase on prices.
They do have a habit of trying to increase DDs on budget scheme as they tried it again last month, but again, a short call to remind them of seasonal consumption did the trick and they kept the monthly payments the same as before. They might not be the cheapest company, but when I phone them I feel like I am talking to a sensible human being and not a robot, which in itself is worth a lot!