Hi, just to update in case you're interested. Swapped my phone yesterday after a bit of a struggle explaining to the guy in the shop that the button didn't work. He spent ages going through all the settings even though I said he wouldn't find anything. He took ages mainly due to the fact he didn't know what he was doing.
Long story, shorter. I now have a fully working camera button, even swapped from a black model, which was a bit dull to the orange, which was my first choice.
Could be a placebo, but the other buttons feel better too.
Again, thanks for your input guys.
(a very happy 930 owner)