Hi, Larry.
I don't know about the combined DVD, but I can tell you that;
Series one DVD has audio commentaries with Lee Mack and Alex Hardcastle on a couple of episodes, as well as an interview with Lee Mack and Tim Vine, and a look behind the scenes at series two.
Series two DVD has commentaries with Mack, Vine, Andrew Collins, and Katy Wix, as well as another look behind the scenes.
Unfortunately, the series three DVD doesn't have any commentaries, but it does have brilliant on location video-diary sort of thing.