Quantitative analysis of material over their life cycles provides crucial insight into the movement of materials within economies, informing economic and environmental impact assessment, and governmental and industrial interventions. Material Flow Analysis (MFA) for whole material cycles is often hindered by data gaps, limiting its practical value. We apply Bayesian Material Flow Analysis (BaMFA) to quantify England's 2019 construction aggregates (sand, gravel, crushed rock) system, reducing the labour-intensive manual data reconciliation requirement of conventional MFA approaches. Despite industry-reported data describing only 20 % of the system, BaMFA fully quantifies the system, provides novel insights into its supply-demand balance, and highlights opportunities for enhanced resource efficiency and waste minimisation. This includes improved quantification of primary aggregate consumption (142 Mt, 68 % from indigenous sources) and landfilling (20 Mt, 96 % demolition waste). This research demonstrates the potential of BaMFA for quantitative analysis of material systems and evidence-based action for more sustainable and resilient futures.