The Data Protection Act 1998 allows you to request copies of any data that mentions your name. 
This data is not simply limited to electronic data – it also includes other records, such as letters, personnel files etc.
The employer has 40 days to respond and is able to charge a small admin fee of up to £10 for sending copies of the information.
The employer must comply with the 8 data protection principles.

The 8 principles are:

• An employer 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.
• An employer must not keep any data for longer than necessary.
• The information must be processed in accordance with the employee’s rights.
• An employer 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.

An employer should avoid processing any data which does not fit these 8 principles.