Then it would seem that you may have been miss-sold a pension transfer, not the original PO pension.
That pension was a final salary scheme, and the Prudential one couldn't have been and certainly wasn't. 100,000's of final salary pensions were fraudulently transferred over into person pensions.
You have probably missed the deadline to make a claim. This link may help though:::::
http://www.financial-ombudsman.org.uk/publications/ombudsman-news/33/review-33.htm
I can enlarge on the differences between final salary pension scheme, and private pension if you wish....just ask !