Environment: Sitecore 8.0 rev 150621
When we are testing our site to get visitor details, GeoIp does not tack City, Region and Country details of UK visitors. But visits received from Sri Lanka get the City, Region and Country details.
Sitecore GeoIp does not track the City, Region and Country visits for the users coming from the internal networks.
To check this you can use an IP changing tool like Hide My Ass or Freedom.