So you want a media centre but you dont have thousands of pounds? The Pi could be the answer! Have a look at the link and work through the instructions, its just that easy!
When it comes to downloading Raspbmc - it has been renamed to OSMC - don't worry about this, just follow the links and download OSMC image for linux. (Don't download the installer!) These can be found here: https://osmc.tv/download/images/