When I have four adults plus a full tank of fuel in my 2010 Octavia L&K Estate ( the boot is empty) there is a scraping noise whenever I go over a bump or over a pothole . It sounds like the noise of a part of the underbody protection and isn't a metallic sound. Two tyre dealers have given the car a good inspection but can't find any signs of a scrape, anyone had similar problems and, if so, what was the solution?

There is plastic spoiler thing behind the front wheel arches that catches when going over bumps when heavily loaded. If you check yours it's probably all scrapped. 

+1 for CWARD

Thanks CWARD, I've just had a look and there are two protection trims about 2 feet in front of the rear wheels that have a serrated lower edge like a comb. This is about the area where the noise comes from but they don't appear to be worn. I think I'll have the rear shockers checked just in case.