Change in Home Location caused by change in router / hub

If you have the WiFi-only iPad (which does not have GPS) your location is determined by the mapped location of nearby WiFi routers. A WiFi+Cellular iPad or an iPhone has GPS and can locate itself.

Without GPS iPad location-finding is done by using a Apple location database which contains the MAC addresses of routers and their physical location. A MAC address is a unique number which is built-in to all network devices when manufactured. No two routers have the same MAC address.

The Apple database is built and updated by Apple GPS-enabled devices (primarily iPhones) actually seeing routers and then adding/updating the router's locations into the database. There is no manual way to request an update to the Apple location database.

Note, to be used for location determination, a device does not need to actually be connected to a router, it just has to see the router and its MAC address. More precise location determination can be done if several nearby routers can be seen.

If your router's location has never been added to Apple's location database your location may not be available to your device. When a router is moved from one location to another erroneous locations can sometimes be reported until the router's location is corrected in Apple's database. The router that you were given has probably seen service in London and was last located there.