Through trial and error, I've found two this week that seem to work:
Swing by Swing:
Free Golf GPS Range Finder | Swing by Swing
myCaddie Pro:
iMakePars - myCaddie
The last one has a course mapper, so if it's not listed, or in my case doesn't show the winter mats correctly, you can map your entire course in about 15 mins.
Turned the Wi-fi off after installing them and they still seemed to still show full functionality. With the tiny bit of battery left (forgot to charge the bloody thing) I went onto the first tee and the yardage was pretty accurate.
I'll give it a blast this weekend and if anyone's interested, I'll post how I got on.