I have a QUESTion
Shadow magic - Can i play single or random missions straight away?
or do i have to get caught up in a campiagn or similar?
any help would be appreciated.

Yes, you can play them straighaway.
But note that all the single missions included with the game are designed for multiplayer.
If you want good single missions there are some excellent ones at http://aow2.heavengames.com/.
It's currently down for maintenance, so you'll have to wait a few days.

You can't go wrong playing random, and you can start playing random maps immediately. Though I do recommend, after sampling a few random races and magic schools, to stick with a combination long enough to learn its ins and outs. Those will teach you a lot about the game in a way that's easy to remember. Highly recommended to quickly try out many variations and work up your different sets of strategies.