I've been removing the slabs that formed a small patio, and while digging throught the very compacted soil underneath, I've found a layer of white material about a spade depth down. It appears to be under the entire patio area, but I've not found it anywhere else in the garden.
It's about the texture of hardened brick mortar, grainy, white and coming up in 3/4inch clumps. It does break down with afew goes with the spade, into smaller lumps and some grainy particals. The soil underneath the layer seems about the same as elsewhere.
From old photos of the garden the patio has been there atleast 8 years, but possibly much much longer. The house was built in the 30's.
The reason I'm trying to describe it is that from the same description my mum is worried it may be aspbestos, and I'd be gratefull to hear whatanyone else thinks it might be.