Only found this out recently so thought I would pass it on in case other people didn't know.
The current number of eligible years of National Insurance contributions in order to get a full state pension is 39 years for women and 44 years for men. This is planned to be reduced to 30 years for both men and women who reach state pension age from 6 April 2010.
I understand that at the moment, the word is that anyone who has paid additional voluntary (maybe also normal?) contributions taking them over the 30 years will not get them refunded, so something to investigate and bear in mind!
Link for info
http://www.dwp.gov.uk/pensionsreform/legislation.asp