I've just realised that as I'm creating new scripts for mods, they are stored in my Data\Scripts folder. Are these required when uploading my mod to the nexus/steam? Or will they be generated on the player's end also?

They have to be included. I think you only need to include the compiled scripts, but including the source files is recommended. That way anybody can have a chance to learn how you did something and anybody can attempt to fix bugs.

As MrJack says; also, it's common to pack the scripts (and other loose files) into a .bsa archive, either with the Creation Kit's own tool or the separate http://www.creationkit.com/Archive.exe utility. This helps resolve conflicts and makes installing/uninstalling the mod easier.

Nice one cheers mate. Is there an automatic way to pack all necessary files, or is it just manually take note of any scripts you used and pack your BSA by hand?

Unfortunately you need to do it by hand. The Creation Kit tries to tell you what you need, but it misses many files.

Best practice is to:

1) Decide on a short (<= 4 character) prefix that you'll put at the start of all the scripts that you name.

2) Set that as the prefix in the Creation Kit's File > Preferences area, and then it will be used for auto-named fragments as well. (If you're working on multiple mods, as I know you are, then note you will need to manually change this prefix, depending on which you are working on.)

Then you can sort the scripts directory by name, and grab just the scripts with your mod's prefix.

That's great that mate good tip