I just received some feedback about this issue from support. But not much that is useful, a cookie cutter reply I suspect....
"Please clear your cache and try again to use the quick fill and related items function. If this does not resolve the issue please respond to this email for additional assistance. Please include as much information as possible so that we may better assist you. Useful information would include:
- Is the the button shaded out? - Do you receive any type of error message? - Any other out of the ordinary occurrence when attempting to use the functions."
As my cache was flushed before I raised the ticket and the problem is recurrent on Chrome, Firefox and Safari I'm more than certain that the trouble is as I first guessed - the full switching on of the new search.
I've never done a Jira and the format looks scary so many thanks Arwen for creating it. I'll try and add my experiences to it as soon as I've figured out how.