yep, i have the "3" 1-2-3 payg sim (bought off ebay and not cut down) in my work phone and works excellent....H H+ pretty much everywhere,the best signal out of all the networks!
i find that if you place a fingernail against the cover at the top of the phone from the screen side and gently push the camera/flash window from the back at the same time,the cover pops off very easily!,oh and great phone by the way! :smile:
update......
some available here in the uk (link)
GENUINE Nokia Lumia 520 Back Battery Cover Cyan Blue | eBay
and here (although refurbs),hope this helps guys!
100% GENUINE NOKIA LUMIA 520 BATTERY BACK COVER REPLACEMENT REAR DOOR | eBay
i`ve been on the actual nokia website and even they dont sell the blue cover!
luckily for me,i bought my one from the cpw in blue,didn`t realise that the "blue" one was so hard to come by! :cool: