Ok, so I finally got round to trying this out... 
So as a test, I told Siri to remind me to open the front door when I got home.
She then asked me to confirm which address for me which I did, but she then told me I'd have to "Enable Remonders in my iPhone's Location Services".
I did this (set it to "Always"), but when I tried the reminder again, I got the same message and when I went into Privacy>Location Services, Reminders was set back to "Never".
So as a test, I told Siri to remind me to open the front door when I got home.
She then asked me to confirm which address for me which I did, but she then told me I'd have to "Enable Remonders in my iPhone's Location Services".
I did this (set it to "Always"), but when I tried the reminder again, I got the same message and when I went into Privacy>Location Services, Reminders was set back to "Never".