I’m interested in giving Sass a go but i’m not fully understanding how to set it up to begin with, i think i’m missing something obvious here…
Everywhere i read says you have to do something with Ruby & Terminal (i’m on a mac) but why when i do almost all of my site building locally then upload online to preview?
9 times out of 10 i don’t run a local server, i write my html/css then upload to preview tweak etc.
Surely anything local has nothing to do with viewing it online?
You would just do the same then :).
In the end all you use is vanilla css and that’s what you upload. You write your css using sass and when you save it a corresponding css file is automatically created. Remember browsers don’t know anything about sass or less. All they understand is normal css. You just upload the css files as usual but keep the sass file as source and you just edit the sass file when you want to make changes and then upload the css file it creates for you.
I don’t use pre-processors myself but I managed to work my way through the sass tutorial on learnable in a day (including installation).
Thank you Paul that makes complete sense and i feel a little stupid now. 
Are there any apps that do what the terminal does just for Sass then, as i always worry messing around in there…
A very common pattern is to use Compass along with Sass. Compass is a friendly interface for those who don’t like command line stuff.