Just to add further information to this story, I contacted cosworth regarding the state of the blocks that they provided and got the following repsonce
The CGI block was a dry linered block that was supplied part finished to
Cosworth. We machined and fitted wet liners to it.
upon further investigation, I have been informed that the CGI blocks that are available to the general public are the same grade material as used by the WRC cars and are available as with and without liners.
The Cosworth blocks recieved additional machining to fit wet liners and other improvements (although nobody would tell me what these are) and all feature wet liners, they are only available to m-sport customers.