It certainly sounds to be a CE.
If the Client’s WI did not specify a type of finish required, then the change in WI to introduce the required finish is a change in the WI. The change will not be due to either of the bullet points in clause 60.1(1) and so is a CE.
If the Client’s WI did not specify a type of finish required, then the change in WI to introduce the required finish is a change in the WI. The change will not be due to either of the bullet points in clause 60.1(1) and so is a CE.