I found this December last year on DVD. It seems to be a more rare release, or in Australia at least.
I had a feeling that it wouldn't be perfect, and I soon found it wasn't (this is only my opinion though, take note.) The first half hour was more like a regular episode tacked on, and if it hadn't been for that, the movie would have run short at an hour, unless some sort of other material had been come up with. However, it eventually becomes more of a "movie", just.
The dinner scene, when the naughty notes passed around end up going to the wrong people was particularly funny. And everyone having to sing when using the outhouse!