So ladies and gentlemen, as I could not find much help on the subject, I present a quick guide to fixing said problem.
Polish - didn't work. I then discovered that the camera is covered by a protective screen which is integrated with the case. So... flea-bay, a Hong Kong distributor of replacement Samsung Galaxy S2 Housings and ten quid later I am presented with a new case.
1. Clear some space and give it a wipe down, don't want any more scratches eh?
2. Prepare your new back plate by cutting up a screen-protector and putting it over the camera lens. I'm going to redo mine at some point, but it will do for now:
3. Turn off and remove the usual gubbins from your phone (battery, sim, sd)
4. Using a precision cross-head screwdriver, unscrew the five screws on the rear of the phone. Use a small magnet to lift them from their resting position and put them somewhere safe (preferably in a layout you remember for their return trip).
5. The tricky bit is always separating the case. Do not be tempted to ram a screw driver down the side and twist, this will just mess up the case. I just used my finger nails and worked it free.
The top is the least resistive and easiest to get your nail in. Work the top loose and then work down each side a bit at a time. You can use your new case as a guide for where the clips are. Be careful not to snap the clips at the bottom of the phone. I was pleasantly surprised that I didn't break anything, and if I can do it, anybody can.
6. You'll notice a couple of things different - strangely, I had an extra electrical connector at the top of my phone, no adverse effects yet.
The speaker system (and probably some other stuff) is embedded in the lower part of the phone.
A precision flat-head screwdriver gently levered on the left will unclip the left side. For the right side pop your screwdriver in from the other side where the battery cover clips into. The speaker part should just pop out.
Mine came out sans-grille. This isn't glued onto the case, so should just lift off, place back onto the speaker component before inserting into your new device.
7. Remove the protective sticker from the inside of the lens screen.
8. Pop the new back onto your phone, starting at the bottom and working your way up the sides evenly.
11. Replace screws, don't over tighten as you may break the plastic threads. Screw lightly anti-clockwise first and you'll feel the thread line up, this reduces the chances of you getting your thread crossed and wrecking it.
10. Remove the button support stickers and other protective coverings
11. Reinstall your gubbins and power up!
12. Snap away
Hope this helps.