So I bought a new toy....a Samsung Galaxy Note 10.1. After a whole load of research into what tablet to buy the Note won on having a pressure sensitive stylus...it's also cheaper than an iPad and has a Micro SD slot, can play flash videos and, well, isn't apple. It's not got the retina screen but to be honest I can't say that many pixels are entirely necessary at this size. I wasn't convinced it would be much better than sketching on my phone with a capacitive stylus but when I went into the Samsung shop and gave it a try with Autodesk Sketchbook I was sold. Sketching on the tablet is really nice, and the tablet version of the App (I got the paid for version which gives you extra bells and whistles) has more options than the mobile version.
I've only played around with it a little, but so far I'm super happy with it....here's what I've been playing with....drawn directly into the tablet: