Can someone please explain the difference between unidirectional and non-unidirectional carbon (if thats the correct term?)..........or is it something I really dont need to worry about??!
Unidirectional or UD as we call it is a 'ply' of carbon fibre with all the fibres running in one direction. You make up 'laminates' by laying these plies in differing directions thus giving you better stiffness in a particular direction/s.
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'Woven' or 'cloth' is this same fibres but woven into a cloth type ply, thus you lay-up two fibre directions at once, this gives you less chance to optimise the lay-up for stiffness.
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Woven tends to be better WRT impact.
Then there's the wallpaper effect- ie, the carbon you see doesn't neccesarily relate to the carbon underneath because sometimes the top layer is just cosmetic. People used to expect weaves, now UD is the thing...
Vortexracing.....thanks, woven it is then, diagrams also help too!
and there is also carbon veil: [img] 
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That's just for surface finish though.
Remember the direction you see on the surface of UD won't mean the stuff underneath goes the same way as the layers are arranged at different angles to optimise the properties. Normally you have 0, 90 and +/-45 degrees used in different amounts and at different levels within the stack.