UK mobile service revenue growth dipped down in Q4, but at least remained still just positive at 0.3%. The dip was driven by contract ARPU weakness at the largest three operators, mitigated by strong ARPU growth at the smallest operator H3G. Looking forward, the sources of weakness (growth of SIM-only and tariff policy adjustments) look more temporary than the sources of growth (data volume growth filling up capacity). SIM-only is likely to hit a natural ceiling, whereas data volume growth has no ceiling in sight and the scope for network capacity expansion is limited. With CK Hutchison currently negotiating with the European Commission in regards to the fate of the H3G and O2 merger, there is a high level of uncertainty on the future of the structure of the UK mobile market. Merging the two networks would generate extra capacity and capability, likely increasing competitive intensity, but the precise form this would take is unclear, as is the future of the brands and the identity of the capacity MVNO recipient(s).