Fiscal and monetary policies
The National Statistics Office's pages for the labour market includes data on employment rates, unemployment rates, training and productivity.
Melliss and Webb's 1997 OECD Working Paper, The United Kingdom NAIRU: concepts, measurement and policy implications (note that this is a 187k pdf), offers an in-depth asessment of structural changes in the UK labour market and their impact on both short run and long run NAIRUs.