Autolycus wrote:

The SLE cladding site has some useful stuff http://www.slecladding.co.uk
but they're not especially cheap.

Regarding fibre cement roofing, I think the main product is Marley
Eternit. Besides roofing sheets, the material is also used for tiles,
slates and cladding panels.

http://www.marleyeternit.co.uk/

The list of stockists for roofing is odd (the list of 'your nearest
towns' doesn't include London!) but the list is more extensive for the
tiles & slates section.
I can recall using Marley's asbestos cement slates in the late '70s,
I'd think they've just changed the material used for the fibre
reinforcement.