What is holding the purlins up at the inside ends?

They go straight into the wall.

The only reason you have purlins on a 10 ft span is that
they are doing something interesting with the dogleg in the roof.

You mean the hip extension? Again I think you could be right.

I've posted more photos showing the purlins going into the wall and
views of the purlins on both sides of the extension;

http://www.photobox.co.uk/album/albu...c_album=727733

Thanks,

John