It's interesting to see that in the UK, in common with other countries with funded pension systems, it's the public sector funds that are at the forefront of shareholder engagement.
The Local Authority Pension Fund Forum (LAPFF) is a coalition of just under 40 local govt funds that have been active for over 15 years, using their shareownership to promote high standards of corporate governance and social responsibility. Lately the LAPFF has been engaging with BP over its recent safety failures, and is about to begin a major shareholder campaign around company audit practices. (The latter subject doesn't get as much attention as it deserves, with the more 'sexy' issue of executive pay usually attracting more interest. However it's worth remembering that accounting practices were at the heart of the big recent corporate scandals.)
There is plenty of good work already going on amongst local govt funds. This is something that the public sector unions could dovetail with very easily. Good to see that Unison are increasingly active here.