U.K. online reseller, Overclockers, has a stock of Radeon HD 3850 cards from HIS, although in saying that, these aren't the lowest priced ones available, as you can pre-order the PowerColor card for £111.61 while the HIS card will set you back £117.49.
Sapphire is going for the same price as HIS, while you have to pay £123.36 for the Gigabyte version and £135.11 for the one from Asus. As all of these are reference cards, we're not sure why there's such a huge price difference.
The only slightly different 3850 on sale is the PowerColor Xtreme PCS version, which is still less than the Asus card at £129.24.
Overclockers is also listing a wide range of 3870 cards ranging from £152.74 for the standard version from PowerColor to £170.36 for the Asus one, with HIS, Sapphire, Gigabyte and the PCS version from PowerColor being somewhere in between the two.
One oddity we found is that Overclockers are calling all the 3850s for Pro and all the 3870s for XTs. We're not sure why this is the case.
You can find the cards listed here