I've got various things set up to hot keys (1-8) however I cannot seem to find a way to set up a hot key for duel wielding my two daggers, can't see anything in the manual about this either, anyone help please?

Just mess with it. On the PC, you set each as right and left with the mouse buttons.
Although I had LR on one line item awhile ago. LR Steel dagger (2).

My daggers are listed seperately on the Q menu, I've messed around for ages but cannot seem to set them to hot key so that i can press 1 key to pull out both daggers.

What does it look like in your item menu?

Same problem

I set up my bow on key 1, duel daggers on 2 and both work fine until I set up a spell on 3 and 4, then when i press 2 to get my duel daggers out I end up with 1 dagger and a spell, its driving me crazy now

i don't think its possible to duel wield both by pressing one button once, but it should equip for each hand if you press the button twice.

I think you are right, I've been loving this game, had no issues at all (Apart from the pc UI needing to be improved, but can live with it) however this seems like a massive oversight on Bethesda's part, the whole point of setting up hot keys is so that you can quickly change weapons / spells, well one of my setup's is duel wielding daggers and I cannot set it to a hot key, very poor!

This site clarifies it, it seems a lot of peeps having issues binding duel wield to a single hot key, so dam annoying, please Bethesda fix it.

http://www.reddit.com/r/skyrim/comments/m8tnk/guide_how_to_use_18_hotkeys_for_items_and_spells/

When I added something else, it would change also. So I just reset it.
Now I have:
1 Dual daggers
2 Bow
3 Torch
4 Spell

It is working fine.

It is possible for duel to be set to 1 hotkey, I've done it, key 1 bow, key 2 duel wield daggers and it works perfectly, however as soon as i set a spell on keys 3 and 4 it totally fcuks up my duel wield on key 2. A bug i guess. Well sadly I won't be playing my duel wielding Assassin until this gets fixed, really annoyed tbh. Reroll tomorrow I guess

So, you guys know that carrying two daggers is "dual daggers." That would make it "dual wield," no? Not "duel wield."

In any event, it works fine for me if I press the hotkey (1-8) twice. Just make sure you add them to your favorites (F from the inventory menu), then from the Favorites menu (Q) assign them a number. Pressing the key twice is preferred, so you can swap one out for a healing spell or something as needed.

Nope it doesn't work, as I said I can set up a bow to key 1 and duel daggers on key 2 and its perfect, don't even need to press key 2 twice to pull out both daggers just once, can play like that for ages and it works every time, but as soon as i set up Heal on key 3 and another spell on key 4, key 2 no longer pulls out my 2 daggers, not even if i press it twice, it pulls out 1 dagger and a spell for some very strange reason. Jeez I hope they fix this.

Aren't you always wielding something in a duel?

It sounds like what's happening for you isn't that you have a dual wield key. You have a single dagger hotkeyed. But when you switch from two-handed to one-handed, it automatically gives your other hand whatever it had last. So if you had two daggers and then went to a bow, and then used your hotkey to get one dagger back in hand, you automatically get the other dagger too. But if the last thing you had in your other hand was a spell instead, then when you go from bow to dagger, you automatically get a spell in the hand that wasn't holding the dagger.

So basically, it's not that it's working sometimes until a spell breaks it. It's just simply not working. You don't have a dual-wield hotkey.