Ok, bit late into the fray, but:

jon CommentTimeFeb 23rd 2008
Unfortunately, in general, Norfolk is not known for having good soils.

Don't go saying things like that, as it's complete and utter nonsense. I'm a chartered SE, in Norfolk (who does loads of barn planning engineering surveys and structural work for conversions as it happens), so I do know what I'm talking about.... ;-)

Did I see mention of an "Asbestos cement roof?" Evocative word 'asbestos', comes under the clients responsibilities to ensure it's safe!

Whilst asbestos cement is reasonably safe and asbestos itself is 'safe' as long as left alone; messing with it, especially if a few tiles or whatever are dropped and cracked, brings out a whole new ball game!! It only takes one little fiber to do the damage and somebody dies, in agony, 30 to 40 years down the line! Chances are it will never happen but.......which is why the HSE get very excited about the stuff! As does the average builder who disappears off site quicker than the proverbial rat at the slightest hint!

You need to walk very softly and get it checked out - it could be very expensive! And the less said about the stuff the better!! Sorry to be a bearer of bad tidings but better to find out now than half way through the build!!