I used phpMyAdmin and a simple SQL update statement to set the existing user ID fields. Quick note - I did not use the username field, as this is what drives the login on my site and I didn't want to change everyone's login. I simply created a custom field called cb_memberid and added the value to that.
I did have to do a series of update statements to accommodate the different length member nubmers (XXXX0001, XXX0012, XX,0123, etc)
Of course! Thank you for that, I was so wrapped up in the wonders of CB triggers that I forgot good old SQL. I have changed all my usernames with an UPDATE.
It still would be good to have a way of performing multiple changes to Users through the backend if anyone knows how. As far as I can see the triggers all work on individual Users one at a time?