When you have added someone to your buddy list, the link in the profile should then change to 'Remove Buddy' instead of remaining as 'Add Buddy'

Hmm, I see what you mean. Yeah, that should be changed.

Also Ross, do you think it possible to have a box in the mini-profile with either a + or - depending on if the user is already a buddy, and when clicked on adds them to your list?

The link in the profile will now change based on the buddy status.