Amazon Certified refurbished Corsair Void Dolby 7.1 RGB USB (exact model CA-9011130-EU).
1 year warranty supported by Amazon so the usual easy point of return/queries. Amazon Certified means that the seller has to meet a certain level of standards to add a degree of confidence (what degree is up to you).
Amazon are selling this new for £69.99 so if you aren't bothered about the box, as this comes in plain packaging, then you make a nice saving of £20.
Corsair offer a 2 year warranty on these when bought brand new, suggesting the build quality is reasonably good for a gaming headset. Reviews seem to echo this sentiment, as a lot of gaming headsets suffer from poor wiring and break after a few months, regardless of price.
All in all a good 7.1 RGB USB gaming headset for less than £50.
Yes I know there's always the HyperX Cloud II for around the same price which sounds great, but the 7.1 mode is a bit lacking. The Void is Dolby certified.
Entirely depends on the needs of the user, I'd recommend (and own) both for their own merits.
Hope this helps someone looking for similar specs in a decent gaming headset.
**edit: available slightly cheaper direct from the supplier for £44.99 if you don't need the Amazon support wrap: http://www.awd-it.co.uk/corsair-void-rgb-usb-dolby-7.1-pc-gaming-headset-factory-refurbished.html