For those who were interested, there is recent briefing note on the DWP website
http://www.dwp.gov.uk/docs/single-ti...nical-note.pdf
This explains how the single tier pension will be calculated with particular reference to how the entlement will be reduced by a "rebate derived amount" for those public sector workers who were contracted out of NI. The way I read it, some of the previous posters seem to be very optimistic and I interpret the rules in such a manner that if you have been contracted out for all your career of 35+years, you will only get £110. (was £107 prior to inflation uplist this month) - no matter how much NI you have paid.
Be warned, you need a degree in gobledygook to be able to understand the technical note on the DWP website.