Despite 5G still being embryonic in its development, there is already a quest for evidence to support decision-making in government and industry. Although there is still considerable technological, economic and behavioural uncertainty, exploration of how the potential rollout may take place both spatially and temporally is required for effective policy formulation. Consequently, the cost, coverage and rollout implications of 5G networks across Britain are explored by extrapolating 4G LTE and LTE-Advanced characteristics for the period 2020-2030. We focus on ubiquitous ultrafast broadband of 50 Mbps and test the impact of annual capital intensity, infrastructure sharing and reducing the end-user speed in rural areas to either 10 or 30 Mbps. For the business-as-usual scenario we find that 90% of the population is covered with 5G by 2027, but coverage is unlikely to reach the final 10% due to exponentially increasing costs. Moreover, varying annual capital intensity or deploying a shared small cell network can greatly influence the time taken to reach the 90% threshold, with these changes mostly benefiting rural areas. Importantly, simply by integrating new and existing spectrum, a network capable of achieving 10 Mbps per rural user is possible, which is comparable to the UK's current fixed broadband Universal Service Obligation. We contribute to the literature by quantifying the effectiveness of the spatial and temporal rollout of 5G under different policy options.