All Winner is a company that makes cheap but capable chipsets, the A10 is their new one and is very capable and very low priced ($7) which is how such a low price point can be gotten for £50.
It's running Android smartphone OS so that means the Android web browser, you can view any website but sites which require plugins on a PC wont work, only HTML5 video will work. There is a Flash plugin for Android but it doesn't always work and development has been stopped so don't expect it to work in the future.
You might want to look at the
MK802,
Z802, those are sticks that plugin to the TV and only have wireless support or go with
Mele A1000/2000 which are set top box based and can take a hard drive, have wired ethernet, HDMI/VGA output. All of those are All Winner A10 devices, there are other Android boxes out there you can get too (like Sumvision Nano boxes) but they arent as open as these ones which allow you to run other software via SDCards.
The only other box with a credible web browser is the Boxee Box (same deal no plugin support), which is more intended for TV usage then Android is.
If looking for a super cheap A10 board there is a guy from the UK selling
them here for £40 with no case just the raw board itself, same as other devices just no casing. You can see other
A10 devices on the XBMC Wiki if you want to go price hunting.