The provision of such time off work is unusual. As there is no legal support for such time off work any provision is entirely at your employer's discretion.
You need to discuss the proposition with your employer. It might be helpful if you could make a business case which would encourage your employer to support your request.
Establish whether your employer has a training and development policy which provides for sponsored sabbaticals, which might meet your needs. If no such policy exists your employer might be prepared to provide such an opportunity, but without pay.
If you wish to take advantage of such a provision you would have to make enquiries as to how you might support yourself and your family financially for the duration of the course.
Your employer might not be prepared to support your request. You will have to consider ways of completing the programme whilst maintaining your employment.
If other work colleagues have been granted such time off for study purposes and you have not been supplied with a satisfactory explanation as to why them and not you, you may feel aggrieved and wish to pursue your claim via your organisations grievance procedure.
