Volcanic ash plumes can present significant hazards to aviation. In response to these dangers, the international Civil Aviation Organisation (ICAO) have assigned nine geographic areas of responsibility to nine Volcanic Ash Advisory Centres (VAACs). The Met Office acts as the London VAAC, and to consolidate its ash and aerosol remote sensing capabilities, it has established a network of 10 combined lidar and sun-photometer installations across the UK. This thesis describes the development, improvement and validation of the remote sensing products from this network. Firstly, I present a set of processing code that I have developed which provides aerosol mass concentration estimates and aerosol classification, together with a web-based graphical user interface that allows non-specialists to process the network data. Next, an updated lidar calibration procedure that I have developed and applied is described. This corrects for offsets between the emitted laser beam polarisation vector and the receiving optics, and is shown to improve the lidar depolarisation measurements. I then compare lidar-derived aerosol mass concentration estimates with in-situ aircraft measurements. For the examples presented, there is reasonable agreement between the two, showing that the network and inversion techniques are capable of providing reliable mass concentration estimates. Finally, I use data from the network in conjunction with other sources of observational data and dispersion model output, to track and characterise two large-scale events that affected UK airspace. Firstly, the passage of storm Ophelia in October 2017 which brought dense plumes of Saharan dust and biomass burning aerosols over the UK is described. Secondly, stratospheric aerosol layers, detected in June and July 2019, are attributed to the eruption of the Raikoke volcano in the north-western Atlantic and North American wildfires. This thesis shows that the network is capable of providing valuable, quantitative information to the London VAAC, and can fulfil its role as a national capability for aerosol remote sensing in the context of aviation safety.