WiFi may be a powerful foot in the door of the mobile market for some cablecos, but the impact of Free Mobile in France or Comcast in the US is not easy to replicate. Liberty Global, which owns cable operators in many parts of the world, has slowed the pace of its $3.9bn UK infrastructure expansion, Project Lightning, following disappointing first quarter results and a reduction in its 2017 outlook. As well as construction delays for Lightning and aggressive price wars in key markets, it blamed declines in mobile sales, highlighting the challenge for fixed-line operators seeking to move into mobile and quad play services. At Liberty’s UK subsidiary, Virgin Media, and German arm UnityMedia, there were particularly difficult results.…