An update (version 1.07) to the contaminated land exposure assessment (CLEA) software has been published at https://www.gov.uk/government/publications/contaminated-land-exposure-assessment-clea-tool.
The update includes the library data sets from the Defra research project SP1010 (Development of Category 4 Screening Levels for assessment of land affected by contamination).
The handbook referring to version 1.05 is still valid as the functionality has not changed significantly. The revised software (version 1.07) has been published under the Government Open Licence which should be referred to for terms of use.