Collyweston Slate can be a costly option. Should your property not be listed or within a conservation area, there can be the option to swap the Collyweston Slate for an alternative, using the removed Collyweston slate as collateral towards your new roof.
The pictures below are a great example of using a replica tile to replace Collyweston Slate. The concept of using graduating tiles in varying shades, sympathetic to the historical environment, on a more cost effective budget.