On Fri, 07 Aug 2009 20:51:42 +0100, Fred wrote:

Should the cavity gap be full of rubble? Should I remove it and what
should I put there instead? Should I plug it with polystyrene and then
concrete over the top or can it remain full of rubble?

I'd remove the rubble, there is small risk that it could form a damp
bridge. If you have some suitable insulation put it in the gap. Think
about damp proof courses and not bridging the cavity when you
concrete over.

--
Cheers
Dave.