Hello,
Like Livers I also have the Tannoy Arena and think it's great. I demod against most of the mid-range "style" packages available currently with a couple of other people, and found it to be the best, and in a different league to the KEF 3005SE in terms of detail and musical ability, (though it should be really as it was originally in the next price class up from the KEFs); while the KEF 5005 matched it more closely for detail, the musicality was still lacking.
Having said that, if you've heard the 2005s and like the sound better than the Arena then I wouldn't let quality issues put you off, as I don't think you'd have loads of trouble. Also, you are covered by the Sale of Goods Act for faults that develop within 6 months, regardless of guarantee, and that contract is with the actual retailer.
Subs do tend to only be guaranteed for 12 months, as they are active rather than passive components, (the Arena sub also only has a 12 month guarantee). The speakers are passive, and have a longer guarantee, though it's a 5 year one for the Arena satellites.
My Arena sub started blowing its fuse a couple of months after I got it, and I got the old one taken away and a brand new one delivered free of charge, (which seems to be going OK - touch wood). Had to hassle the retailer a bit to take away the old one for free, but they did eventually, (and have to really, as it's in the Sale of Goods Act).
Hope the above helps in your decision.