Deneb

This is the best one you have posted martyn, clean field with minimal gradients. Looking at this it seems you are suffering from some field rotation of the stars, I presume this was unguided but anyway this points to polar allignment being off

Thanks Keiran, yes, it is unguided (that'll be my next want :)). I think any field rotation might be lens distortion? If the polar alignment was off, wouldn't there be trailing in the centre too (given that this shot is of Deneb i.e. virtually overhead) ?

What gets me is there is no color at all. A lot of shots I see (yours and other people) have a lot of nebulosity in them. Is this done with filters, processing, or is it natural?

The nebulosity comes with time, 2 minute exposures on a DSLR and I presume its unmodded wont capture much if any, if you shot at a particulary bright target such as orion M42 then you will see the nebulosity apear, but generally to capture the fainter type backgroun nebulosity ( like that around deneb) then long exposures are needed. If polar allignment is off the image will appear to rotate around its centre, the stars in the centre stay round and the outer ones rotate around it, a bit like star trails

There is a lot of nebulosity around the star Sadr which is near deneb, if you shot for this and took longer and more exposures then you should see something and the more exposures you get will help smooth the image out. Aim for at least 20 subs at the longest exposure you can get without trailing and then stack and process and see what you get. The more subs you get the easier it is to create a better final image.

Sorry, shaunster, misnamed you! Thanks for trying to help. Yes, my canon 5d is unmodded and this is a 4 minute sub of sadr and m29. Hard to believe that I can get anything nice with subs like this. ISO too high maybe? Also, have to get into drift aligment :)

Looks very noisy yes, but this is why you need loads of subs to overcome this. Also with the DSLR being uncooled and this the middle of summer your images will be additionally noisy