Thanks for the "Thanks"
I'm in the same boat as you guys, I've already upgraded to KitKat so I don't actually have any of the old JellyBean app versions anymore on my T310.
I obtained the file I posted above from asking for it on another forum which somebody kindly extracted from their device. I tried to install it myself but had no joy, but thought it worth posting here for others to try just in case.
It looks like we are not going to be able to revert to the old video player, and getting the Dolby function back again will be a struggle, maybe not even possible, which is a shame. Having the Dolby feature made media playback using the built-in speakers sound so much better.
Other than the missing Dolby, my installation of KK is running pretty good, I'v made several system tweaks and removed a huge number of the Samsung apps to make it leaner. The first thing I had to do was turn off the stupid KK permissions for the SD card so that it is accessible fro all apps and works like it does in JellyBean.