Hi guys I'm planning on making a companion mod to use for one of my characters soon and I was just wondering what the best most up-to-date companion base is to use?

http://lovkullen.net/Emma/Comanion_project.htm#Companion_Project_v31 would be the latest companion template that I know of. If you want more advanced or specific functions, you can always open other companion mods like Kateri's Julan, Jac's Jasmine or Melian's Comes-By-Road to have a look at their scripts too.

Grumpy's template is as good today as it was ten years ago, as far as I'm concerned. It offers me everything I need to make a bare-bones custom companion. I'm actually pretty fond of basic companions like this because they allow me to use my own imagination.

But if you are looking to create a more fully fleshed-out companion I'd second HangHim Higher's advice to poke around inside the inner workings of companion mods by Kateri and Emma and others to find out how the masters and mistresses do it.

There's also http://www.gamesas.com/topic/1502430-wip-mwse-companions-template/ if you want to go the MWSE route.