I found a workaround for this with a couple of hints from krileon on another topic thread. Thought I would share it for anyone else who was looking to do something similar.
Basically I ditched the idea of using CB connections for users to flag other profiles as favourites. Instead I created a profile field where favourite profile ID's are being stored as a comma delimited list.
To add to the list I have a Add_to_Favourites field which displays as a link to a autoaction on profiles by setting the "Profile Value Layout" parameter like below...
<a href="
mycbsite.com/dev/index.php?option=com_comprofiler&view=pluginclass&plugin=cbautoactions&action=action&actions=97&Itemid=181&fav=
[username]"><img src="images/site/icons/fav-plus.png" alt="Add to Favourites" title="Add to Favourites" height="32" width="32" /></a>
Display of the field is controlled by CBConditional which checks [cb:userdata field="cb_profile_favourites" user="#me" /] to see if it contains [username]
Notice I added the fav=[username] query string to the url calling the action which sends the target profile (to be favourited) id to the action.
The action is a Field type action with no other triggers. I set the conditions to check that the target profile id passed in the query string [get_fav] is not already contained in my cb_profile_favourite_members. Assuming it's not then the action suffixes the id to the end of the comma delimited list.
To remove favourites I follow the same method in reverse.
Chuck in a list filtered to only show users in the comma delimited list and I have my favourite profiles feature.