Employment references are covered by an exemption under the Data Protection Act, so you have no right to require your former employers to let you view the contents. However, your former employers could let you see it if they chose to do so. (i.e. it's not illegal for them to let you see it but they can simply say 'no').
However, you might have the right to require someone who has received the reference, and retained it, (such as a new employer) to divulge the contents.
The Information Commissioner (who is responsible for ensuring that individuals and organisations comply with the Data Protection Act) has issued a 'good practice' document, relating to employment references. When reading it, you need to take care to separate out legal requirements from the advice given by the Commissioner (which is not a legal requirement):
http://www.ico.gov.uk/upload/documents/library /data_protection/detailed_specialist_guides/su bject_access_and_employment_references.pdf
Chris