The current edition of the Economist carries an article on union decline and claims that social movements such as London Citizens are 'in some ways... taking the place of trade unions - which these days have programmes but little power.' This superficial theory ignores the fact that unions such as UNISON have been and continue to be integral to Citizens, and in the case of its forerunner TELCO, East London UNISON branches and the UNISON General Political Fund were instrumental in putting it on the map:
http://www.economist.com/news/21567424-trade-unions-are-beginning-learn-community-activists-fight-glower
The article goes on to counterpose the posturing of 'left led' trade unions who give a primacy to industrial action with supposedly 'modern' unions who have a constructive and co-operative relationship with employers. The inconvenient realities are that the same supposedly 'left led'unions have in recent years been first to spring to the defence of the neo-liberal EU and opposed reductions in military expenditure at TUC Congresses and that the union-management accord at Tesco is the epitome of company unionism - and not mirrored in Tesco's attitude to unions outside of the UK.
The real story about union decline is the continuing hemorrhaging of union membership in the private sector and the urgent need for unions to unionise the fast growing private services sector of the economy as well as for an incoming Labour Government to remove legal barriers to union recognition by scrapping thresholds that enable employers to block organising efforts.