Okay, so I used a couple of methods together for this.
The first method is the 'Sony fix' -- search for 'surface panel calibration tool' - the download you're looking for is called UNOOTH-P0112513-1082 with an MD5 of 91514542bdf87898ea24dfe4add0548e.
The second method (which surprisingly no-one on the internet has suggested) was uninstalling the touch drivers!
Here's the combo I did that worked, but please bear in mind that I can't verify that its neither one nor the other that would sort it out in isolation:
1) Uninstall the touch drivers -> right click Start -> device manager -> right click HID Compliant touchscreen -> uninstall
2) Touch your screen to make sure the drivers have gone
3) Run the panel tool
4) Back in device manager, file or edit (I can't remember) -> scan for hardware changes
5) profit.
I really hope this helps someone out there. Its an annoyance at best, but if you're borderline OCD about certain things then you'll breathe a sigh of relief