Okey, bizarre follow-up.
I'd done nothing to fix this. Was thinking of backing everything up, doing a factory reset and then, if it wasn't fixed, take it back to the shop. But yesterday while sitting on the bus home I idly went through the "handle your apps" section (my phone is in Swedish and I forget what it's called in English). I did what I often do, I force a stop to programmes I don't want (like stock info and the weather app) but can't get rid of unless I root the phone which I'm do scaredy-cat to do. Anyway, force stop, delete all settings to them or whatever it's called (just because it annoys me that they're running when I didn't start them and don't want them). I didn't do this to ANYTHING remarkable. Maybe to Footprints, which I don't know what it is. I've done this to Footprints before though to see what happens and nothing did.
So I back out of that, and the phone reloads a little, like it does. And when home screen comes back online it's COMPLETELY DIFFERENT. It's like what it looked like when I first got the phone. My chosen background - gone. My links to favourite apps - gone.
A moment of panic.
Then I check if they're actually gone off the phone, but they're not. Everything is there.
I check the camera. It turns on, but the flash is gone (i.e. very dark photos). I fancy it makes a very faint funny, protesting noise.
The flashlight doesn't work.
I am so befuddled. This is so strange.
I've been reading threads on various forums but I really don't know what to do. Seemingly factory reset doesn't always work? Today it came with another upgrade and I deleted six apps so I could manage that 