In stock. Best be quick as the stock level isn't shown! This is a great price tag as they are like brand new. Next cheapest (brand new) is £54.99 at Argos.
No top-up required (although o2 insist you select a payg tariff). You can just use your own o2 sim. If you want to use it on another network, check ebay for unlock codes for the LG K4 :)
Some info from o2 about like new phones:
Perfect phones look like they've hardly spent any time out of the box. They're like brand new phones, just not in their original box.
They won't have blemishes of any shape or size. We install the latest operating system and you'll get a 12 month warranty to put your mind at ease."
Find out more info on the spec at gsmarena