The growing importance of subsurface carbon storage for tackling anthropogenic carbon emissions requires new ideas to improve the rate and cost of carbon capture and storage (CCS) project development and implementation. We assess sandstones from the UK Geoenergy Observatories (UKGEOS) site in Glasgow, UK and the Wilmslow Sandstone Formation (WSF) in Cumbria, UK at the pore scale to indicate suitability for further assessment as CCS reservoirs. We measure porosity, permeability and other pore geometry characteristics using digital rock physics techniques on micro computed tomographic images of core material from each site. We find the Glasgow material to be unsuitable for CCS due to very little porosity---up to 1.65%---whereas the WSF material showed connected porosity up to 26.31% and permeabilities up to 6040 mD. Our results support the presence of a percolation threshold at 10\% total porosity, introducing near full connectivity. We find total porosity varies with permeability with an exponent of 3.19. This provides reason to assume near full connectivity in sedimentary samples showing porosities above this threshold without the need for expensive and time consuming analyses.