Background Children with intellectual disabilities and behaviours that challenge (BtC) and their families require complex, multi-agency support. Despite policy commitments to strengthen community-based provision, including those arising from Transforming Care and the forthcoming Mental Health Bill (2025), there remains limited evidence on how these services are configured or what they cost to deliver. The National Institute for Health and Care Excellence (NICE, 2018) identified major evidence gaps in optimal service design, integration, and cost-effectiveness. Objective This research explores the structure and associated costs of community-based services in England that support children with intellectual disabilities and BtC. It aims to describe the configuration of local “service models”, identify cost drivers, and clarify data requirements for commissioning and evaluation. Methods Within the NIHR-funded MELD (Mapping and Evaluating Services for Children with Learning Disabilities and Behaviours that Challenge) programme, 278 services were identified across England. Using survey data (n=161), Latent Class Analysis and descriptive synthesis produced a typology of five community service models. Nineteen representative sites participated in a detailed costing study using a bespoke data collection instrument aligned with national unit-cost frameworks. Quantitative and narrative data on staffing, pathways, and overheads were analysed descriptively and thematically, with input from a Parent Advisory Group. Results Five distinct service models were identified: generic CAMHS, ID-CAMHS, Children and Young People’s Disability, Specialist BtC Support, and All-Age services. Costs were primarily driven by staffing mix, intensity of BtC support, and organisational structure. Considerable heterogeneity was observed in funding flows, eligibility, and waiting times. Conclusions This study provides the first national overview of community service configurations for children with intellectual disabilities and BtC. The findings highlight significant variation in organisation and cost, informing future economic evaluation and service-model optimisation in line with ongoing policy reform.