Just went round to my dealers to get some parts, and he told me how they have so far failed every single one of the '07 MP3s (and a few '08s). All had one particular issue - the adjusting ring on the rear shocks had a crack. We went outside and looked at mine - yup, each adjusting ring had a crack.
We reckon using ACF50 every six months on these unprotected alloy rings should prevent this - as it looks like the cracks are due to corrosion causing a weak point, and bottoming out can then break the ring. With one crack the shocks still work - with two the ring would fly off and the spring would suddenly fully extend.
So as these aren't repairable it's GBP200 for a new pair of shocks. They've done five years heavy duty, so I'm not too disgruntled.