How do people manage to get their corrugated roofs looking so good?
I'm not sure that this reply is going to be very helpful but I have used a vacuum-formed plastic product supplied by Garden Railway Specialists (of Princes Risborough). A large sheet includes two panels of corrugated iron, with boltheads and overlapping joints moulded in, each about 114mm by 400mm, that are just the right width for a wagon roof . . .
The bit I have leftover still has the (faded) label on, with the product reference LSA2 (I think) but the grsuk website doesn't still seem to list it (which is why I'm thinking this reply may not help too much).
From memory, there was also a strip of ridge tiles on the same sheet, so the product was almost certainly intended for the roof of a building.
Of course, for indoor buildings (for an exhibition layout, for example) , you cant get cheaper than than a roll of (single-sided) corrugated cardboard . . .
(so
that's where those plastic ridge tiles ended up!)
All the best
David