Backstory.
Moved house one year ago, brought existing telecom router to new house. iOS devices think they are still at the old house.

The issue occurs on multiple up-to-date iDevices (iPhone 6+, 5s and and iPad 3rd gen)

When I open Google Maps (or Maps.app, or Geocaching.app, or perform some location aware task like taking a photo) my iPhone thinks we are at our old address. (This is the most frustrating part as many photos taken at home are geotagged wrong). This happens when connected to wifi. If I then turn off the wifi; the device will [eventually] realise its correct location.
I can actually watch the maps locator slowly move from one location to the other.
Also using a MacBook Pro (10.10.1) the Maps app will shows the incorrect location. Google Maps in browser cannot determine a location.

I have tried:
Resetting the devices (issue occurs with brand new iPhone 6)
Restoring the router to factory settings
Updating the location of the wifi AP on the Skyhook website (successfully, but have been advised by Skyhook that they are no longer the default provider of location info for iDevices.)
Contacted Skyhook for support
Contacted Apple for support (they have advised contacting my ISP)
Contacted Spark, they are very pleasant and helpful but the rep I have been speaking to cannot explain why this might be happening)


I am 99% confident that a new router would work correctly, as presumably the AP would be a newly registered device at the correct address.
But why can't I fix this?

Cheers,
Joseph