I have just started my first game and have set a weapon and some spells to the hotkeys. In the favourites menu I have set my sword to the right hand and fire spell to my left hand there have been occassions where I have ideally wanted to change spell in the hope that it swaps it out of my left hand but it hasn't. Every time I have tried it equips the new spell in the right hand, leaving me with 2 spells and no sword.

How can I set it so spells swap in the left hand only? I would rather just press a number than have to bring up any menu on the fly.

... Never mind. I think I was mistaken.

I think since you mentioned hotkeys, are using SkyUi? If you want spells to go to your left hand, hold the button that you have that uses your characters left hand(most cases the left mouse button) and press the number where you have your spell. That has worked for me.

Boy do I feel dumb. Thanks for the tip this has been bugging me for ages!

Does that work for weapons, too? Just curious

As for the other, tap the hotkey TWICE for the spell and you have that spell in both hands, THEN tap the weapon hotkey and you are set

Yes it does! Just make sure to have the side(Left/Right mouse button) you want to equip the weapon/spell pressed when you click on the hotkey.