There are a number of mods that require you to start a new game... and while I'm not planning on restarting just yet - I will at some point in the future... The thing is, it's a shame that it may leave me unable to play my original, and first - character. It would be a shame that, it being my first character - and I (I know it sounds a bit silly) feel slightly attached to them, if you know what I mean - I'd not be able to ever just reload the save for nostalgia purpose, etc. So... would there be any way to play on my old save without it messing up both that save and the newer save?

If you can, use http://www.nexusmods.com/skyrim/mods/1334/ Mod Organizer to set up your current character and your new game with their own individual profiles. Then whenever you want to check in with your old character it's just a drop menu away.

That's probably a safer way to do it than to just deactivate the newer mods manually, as any loose scripts installed with the new mods could still find a way into your old save, even if you are not playing with them.

Thank you! This sounds perfect! It looks like it may be a bit... hard to get my head round, but I'll consider installing it when it comes round to retiring ol' Silva'al.