Bought from Ffordes, but if your lens comes with any fault at all, ask for a full refund (they have a 7 day cooling off period) and return, don't bother going down the route of fixing it under their 6 month warranty. I had a lot of grief when I tried this with a Canon 24-70mm f2.8 lens I bought - it was fairly old though (2003).
Ask them for the manufacture date code from the lens before purchase, as CPS told me not to bother continue to try and sort it out, as it was pretty old, and couldn't verify how many previous owners had the particular lens, and repair costs could outstrip the benefits of buying 2nd hand.