It is not possible to recommend an energy supplier to someone when you don't know their circumstances (e.g. size of gas/elec bill) or what is their attitude to the future - "pessimistic" (e.g. prices will go up) or optimistic (e.g. they will go down) and whether they are risk averse (e.g. they would rather have a fixed price) or not (e.g. they are happy tol gamble on a variable rate that may come down).
Having covered my backside on this in case things go wrong ......... I thinkthe EDF Blue + Price Promise is still on offer. This is fixed rate but with no penalty for moving companies in a few weeks or months if something better comes along. I would also compare it with Scottish Power's fixed rate offers. If you are looking for variable rates, I haven't looked at these and can't help you.
Probably best to visit one of the comparison sites such as uSwitch, MonetSupermarket, or EnergyHelpline. Obviously you will need to make guesses about your future usage. Are you moving into a bigger or smaller house, and are you moving from the cosy south to the icy north? In most cases, but not always, you get the best deal by opening your account via internet and paying by Direct Debit. Often dual tariff is also good.
Hope some of this helps.
P.S. To get the best cheap rate fixed deal I think you need to move now. I think Scottish Poer have already removed their current offer from comparison websites.