The Data Protection Act 1998 states that you must allow your employees copies of any data that you hold on them. 
This data is not simply limited to electronic data – it also includes other records, such as letters, personnel files etc.
If your employee requests copies of any data you hold, you must respond in 40 days.  And you are able to charge a small admin fee of up to £10 (in 2011) for sending them copies of the information.
When you record and store data on an employee, you should ensure that you comply with the 8 data protection principles.  Failure to do so could go against you at an employment tribunal.

The 8 principles are:

• You must process and data on your employees fairly and accurately.
• The information held must be accurate and up to date.
• And adequate amount of data must be held.
• The data must be relevant, and not excessive.
• You must not keep any data for longer than necessary.
• The information must be processed in accordance with the employee’s rights.
• You must ensure that all information held is secure.
• The data may only be transferred out of the EU if there are adequate levels of protection.