The answer appears to be no, however information is rather patchy, if you know better, please let me know.
In 2009 the 'Jan Grieg-Gran' website was replaced with the 'SailRacer' one, released at the 2009 Worlds around the end of July. However, there were a lot of problems getting the new MCA Webmaster (Peter Sedgewick) the required level of access to the new system. By mid-September, the 'SailRacer' website system was abandoned, and a new website, using the Joomla! Content Management System was created. Peter chose to write his own event system (i.e. an extension). We still have the php code for this, however, we don't have access to petersedgewick.com which is where the sql database storing the data was hosted, so I can't go back and look at the website calendar for 2010 (we now use a Joomla! extension 'Jevents' for our events calendar).
There was no 2010 Yearbook (although some work was done towards compiling one, but a calendar was not part of this) and no issues of Reflections were produced around this time.
I've found this document '2009 - 2010 Mirror Class Association events' which was last changed 14th November 2009. It lists the 2010 Nationwide series as having the events at Chipstead, Brightlingsea (Nationals), Blithfield (Inlands), Annandale, Mount's Bay (Westerns). The NOR for the Chipstead Nationwide makes no mention of it being the Southern Area Championship.
There was a Southern Travellers series in 2010. One might imagine that, if there was a Southerns in 2010, it would be a Southern Traveller event. The Chipstead Nationwide is not listed as part of the series. The poster does not mention any of the events as being the Southern Areas. Of the events listed, only Poole, Itchenor and Warsash are two day events (one might imagine that, if an event was going to be the Southerns, it would be held over two days). Itchenor hosted the Southerns in 2009, so it seems unlikely they would host in 2010 as well. The Poole YC event is TBC on the Travellers poster (suggesting it's a late addition), and I have found the poster for the Poole event which, it turns out, was the Annual Poole YC Regatta. Again no mention of is being the Mirror Southern Championship. There is an event report of the Warsash event, but no mention of it being the Southern Areas. There is no mention of a 2010 Southern Areas on Yachts & Yachting or SailRacer.
Hence my conclusion, it was not held.