The company I work for has offered an improved benefits package to new starters which has not been offered to existing staff. Are they legally entitled to do this?

The company I work for was  bought in April 2008. Employees of the Company that took us over were entitled to inclusion in their company pension scheme and 25 days holiday per annum

We were told that our Terms and conditions would remain the same i.e. 21 days holiday per annum and no company pension scheme. I understand that the new company was under no obligation to extend these benefits to us.

However, I have since found out that they have taken on two new people who have been included in the company pension scheme and offered 25 days holiday. The company do not know that I have this information.

 One of these new recruits was taken on as a manager in May 2009, the other as a product manager, which is an identical role to myself, in April 2010

If the company is not entitled to do this what steps can I take to address the situation?