The UK population is ageing. This demographic trend is challenging for existing infrastructure and services because older people have specific daily activities and mobility patterns. Moreover, the older population is highly heterogeneous regarding demographics, health conditions and transportation access. While agent-based models are increasingly used in urban planning, they generally ignore this heterogeneity in elderly populations. This paper presents an agent-based model to support urban planning related to seniors in the West Midlands county, UK. The model is built and validated using mainly open data. Its potential is illustrated on the example of elderly healthcare accessibility.