Crumbs, I haven't posted here in ages. I'll have to start doing it again, posting issues and solutions to issues as I come across them...
So what is happening?
Lync 365 / Online client is now currently being moved over to Skype for Business (as of 18 May 2015), which is causing all sorts of hassle for many people. But it shouldn't. Honest. Skype for Business (SfB) is just a replacement to the Lync 2013 client we have all come to know and love... But don't worry, the new SfB client is a slight change in look and feel when working with it, and has a few neat extra features when using the new client.
Sooooo Skype themselves have written an article to make sure people know the difference between the SKYPE client and the SfB client, have a look - https://support.skype.com/en/faq/FA34551/what-s-the-difference-between-skype-and-skype-for-business. We (Microsoft) have also written an article describing the differences and the changes to Lync online when it becomes SfB (I think the word "online" is assumed here) - https://technet.microsoft.com/en-us/library/dn913785.aspx.
That last article goes through the differences in the two types of clients and features new interfaces and features.
Don't get me wrong though, you can still use your Lync 2013 clients if you want to. If you are struggling with controlling the "click-to-run" updates which come through automatically for each PC and you want to centralise the updates from a server on your network (in affect chosing when and where the updates come in), go here for more information - http://www.microsoft.com/en-gb/download/details.aspx?id=36778.
If you want some advice in controlling the Skype for Business client experience, then look here http://blogs.technet.com/b/scottstu/archive/2015/04/13/controlling-the-client-experience-with-skype-for-business.aspx. A great article and explains most things....