I returned it in the end. Got the replacement today. It didn't seem to affect the camera but I thought if I'm gonna live with this phone for 12 months or so I want it to be right. I know it's a cheap phone but I expect it to ship without a load of crud behind the screen. The battery was also shocking so hoping for better this time round.
I actually wish there was a way to block that camera. I used a small, black-colored thin plastic on my old Sensation 4G, but that was facilitated by the back casing overlapping the top front of the phone, holding the plastic tightly and unnoticeably.