Public Health England has a solar network which has been established for over 25 years which measures erythema effective UV, UVA and photopic radiation. At the Chilton site there are erythema effective solar UV data available for 25 years from 1991 to 2015. Until October 2004, the data were gathered using a Solar Light R-B 500 radiometer (SL-500), which is not temperature regulated. From October 2004, the data are from a temperature regulated Solar Light R-B 501 radiometer (SL-501). A temperature correction model has been developed using overlapping SL-500 and SL-501 data from 2006 and verified using overlapping SL-500 and SL-501 data from 2005. This correction has been applied to the non-temperature regulated SL-500 Chilton data from 1991 to 2004 resulting in a 25-year dataset of SL-501 equivalent data for the analysis of long-term trends. The development and verification of this model is described.