One for the forums, as I can't find the error on Google or Bing, and being a home lab it doesn't really warrant a support call...
I've set up Host Profiles in my vCenter server, extracted from a host (192.168.2.51). I've added other hosts to the cluster and successfully remediated those, and changed settings in the host profile and successfully remediated the source host. But then I decided to remove and add the 192.168.2.51 host back using its FQDN, which seemed to require me to disconnect it from the VDS's that it was attached to. Having then removed it from the cluster and rebooted I added it back and went to remediate it to get the port groups back the way they were and I got the following error:
The remediation cannot proceed, because the deferred settings cannot be extracted from the selected hosts.
I can't find any mention of this error online, and I've tried resetting host customizations, checking host profile compliance and rebooting the host and the vCenter server (and again in varying combinations). I suspect it may be due to the fact this was the host I pulled the host profile from, and have now effectively renamed by adding it back using its FQDN, so the answer is probably to extract a new host profile from a different ESXi host and remediate using that - but I thought I'd first throw this out there in case the solution helps someone else, and the solution may be a good learning point, which is the whole reason for a home lab in the first place.