Good post FrostC
I think the main worry is that the CG will be an additional escort task on top of the already very thinly spread deployment. In some cases the CG will replace the current vessel deployment but not all - hard to see it being used chasing drug smugglers in the W Indies for example. But I guess you could argue that an enhanced River Class (or something like the Omani "Khareef" class) would be a better buy for that sort of job anyway.
PS - we could aslo do with a few more Astutes if one is going to be attached to the CG......