Browsing eBay I came across this Octy MK2. Only a few months older than mine but never seen rust like it?! 

 

Is this to be expected for all of them in due course? 

 

Mine has a little on one sill and the odd tiny blister.  I have pumped both sills full of lanoguard to hopefully keep it at bay as long as possible. https://www.ebay.co.uk/itm/185796682982?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=bBJq1NtKQQa&sssrc=2349624&ssuid=cUmldqScSL2&var=&widget_ver=artemis&media=COPY

"I do like to be beside the seaside.............."

If that's what's visible I imagine the running gear is ready to crumple.

I can believe it, mines a 2007 vrs 170. Both sills quite badly corroded and the tail gate almost corroded through where the number plate lights are. But surprisingly its totally solid underneath.....but saying that mine has done 216,000 miles and seen a fair few winters.

This is very common in Estonia. Even Mk3 are beginning to rust.