Thanks for the replies - very useful!
I'd rather take fanless 8" over haswell 10", so that has helped a lot.
So my revised requirements are:
8"
Bay Trail
GPS (AGPS won't cut it for me)
Cellular
Ideally, HDMI out
So far, I've come up with:
Lenovo Miix2 - no HDMI out
Toshiba Encore - no...