OK, that is the UK version of the Sony Store (WH Smith)
The image below has an arrow pointing to where it asks for you to register your Reader.
click to enlarge
Once you enter, it should have a place up top to sign in and register.
By the way,did you know that MR has free ebooks? They have been beautifully handcrafted by some very dedicated MR members. (I think the MR free books are better formatted than the free classics from Sony.)
ePub format and
Sony BBeB / lrf format
Free ebook sites..
feedbooks.com and
manybooks.net
Free and for purchase ebooks ..
smashwords.com and
baen.com Plus Baen has a
free library
You can explore using
Calibre to manage your library of DRM free books and Kovid, the creator, frequents the forums here. We even have a dedicated
Calibre forum.
Here are a couple of book search engines for finding and comparing book prices..
AddAll and
Inkmesh.
PS Check my signature and click on the links to find more information.