Some responses for you Philip:
"Will these all be updated to be non-UK companies but with blank details in the law governed and legal form elements?"
Yes, that is the intention.
"Similarly what information will be included in the Company Data Responses for such corporate officers that were originally EEA companies and are now non-UK companies?"
If this refers to information returned on those officers that we have moved across, then (as above) they will only show Place of Registration & Registration Number, until they sent us the additional information.