How do my group members have their own ID's displayed when they alter the wiki, at the moment all changes are under my (the moderator) email address even though they have made their own contributions? We are currently using the free wiki for a group presentation - do we have to pay and upgrade to get individual's records of work?

You should be able to see changes attributed to particular users if you have your group members create their own PBwiki Accounts.

To do this, have them go to http://my.pbwiki.com and create an account.

They can add your wiki from their My PBwiki page. They will need to enter the wiki invite key (previously known as the wiki password) to tie your wiki to their PBwiki Account.