Changing Energy Suppliers

[Im a BusyBee]

I have been looking to change electricity supplier (we do not have gas) i can apparently save approx 25% by changing to OVO - i have never heard of them?!! The reviews are mixed and im just wondering if anyone can offer any comments of their own experiences in changing ie any company to avoid or any particularly good? we have always paid by cheque for a quarterly bill - are monthly direct debits ok? I dont like the thought of not being in control of what they take. Also i am hearing M + S are competitive at the moment but they are not coming up on comparison websites? Any comments or info would be much appreciated.