Thanks for your quick reply, is this most likely to be down to...

cooling?

lack of power? (I'm sure I read in this thread somewhere that normal USB ports dont provide enough power by themselves and they should be put through a powered hub? Are yours in a hub?)

or should I try running it at 0581 or even 0781 just to see if it changes the HW rate as it is? What do these things run at if you dont specify a frequency?

I've also noticed that the speed fluctuates regularly, although it's averaging at around 1.363gh/s, watching the (5s) in the top left hand corner, it drops down to 600-800 mh/s then up to over 2 gh/s, should this remain relatively static or is it normal for it to fluctuate like this?

Another thing to point out in case it's made a difference, is that there are two versions of cgminer on the link from the pdf guide:

https://github.com/AntMiner/AntGen1/tree/master/cgminer

And I'm using the newer version - cgminer-run-windows-20131224.zip rather than the 20131222