cf-leeds laid this down on his screen :
I thought I'd just look online for some galvanised corrugated metal sheets,
around the same dimensions at the old asbestos, but I find there are many
products out there, including corrugated bitumen sheets.

Can anyone offer some advice on a good option here.

The modern equivalent of the corrugated galvanised metal, is a squared
box section, galvanised and painted in various colours. It comes in two
thicknesses, get the thicker one - less chance of it denting. Also get
the special self sealing bolts/screws for it.

You can get plain or ready insulated underside.

A very easy DIY job, with probably no need to cut the sheets. If you do
need to, the maker suggests cutting with a scissor like implement,
which will seal the cut edge with galv..

I did both my garage and workshop roofs with it, 10 years ago - no
complaints here.