I Colin,
I also own a HS 700D. I haven't had any problems with the return to home. What I'm having problems with getting to work is the follow me feature. So maybe we could help each other out?
What I have noticed is that I need to do a gyro calibration after each time I power off the drone. Are you able to successfully do the gyro calibration? Before you take off, the front lights should be solid red and the rear lights should be solid green. I also notice where I fly I typically get 15-17 satellites locked on. How many satellite locks are you seeing on your remote?
Just an observation. When I press the return to home button on the remote, it will immediately start coming back to the location where I took off at, but when it reaches that area it will tend to hover for some time before it starts to descend for landing but if I wait long enough, it does gradually start to descend and land.
Is follow me been working for you?