The UKCP18 exploratory regional time-mean sea level projections are based on a two-layer energy balance model (e.g. Gregory et al, 2015) fit to individual CMIP5 climate models. This model framework is used to provide extended projections of global thermal expansion and global average surface temperature (GST) change to 2300. Global contributions from ice sheet surface mass balance and glaciers are related to GST following methods described in IPCC AR5 WG1 Chapter 13 (Church et al, 2013). Global sea level contributions for dynamic ice discharge for Greenland and Antarctica are based on extrapolation of IPCC AR5 projections to 2100 and the modelling work of Levermann et al (2014), respectively. Estimates of land water storage changes follow those reported in IPCC AR5 for the 21st Century extrapolated to 2300. These global components are regionalised for the UK through use of: (i) sea level fingerprints for mass components provided by Aimee Slangen and Giorgio Spada; (ii) regression relationships around the UK and across CMIP5 models for the oceanographic component; (iii) an ensemble of estimates of the relative sea level change from glacial isostatic adjustment from the NERC BRITICE_CHRONO project. Please refer to UKCP18 documentation for detailed methods.