There is a huge industry on this:
I googled pensions ombudsman and got:
Pensions Ombudsman - PowersPeople, and bodies such as trustees and employers, can ask the Pensions Ombudsman to decide complaints and disputes relating to the running of pension ...
www.pensions-ombudsman.org.uk/powers/ - 17k - Cached - Similar pages
[ More results from www.pensions-ombudsman.org.uk ]
and sort of start there and work down
This type of thing has DEFINITELY occurred before and there will be a path to follow
Off the top of my head:
first of allcomplain to the pension fund you made the contribution to
and this should be in writing
and then follow their own complaints procedure
this is called exhausting local remedies
then go public to the ombudsman
don't sue it will cost you money
although as the lawyers say - on the facts disclosed, it does seem as though you have a cause of action