You are protected at work against age discrimination by the Equality Act 2010. The Act applies to employers, private and public sector vocational training providers, trade unions, professional organisations, employer organisations, and trustees and managers of occupational pension schemes.
Age discrimination is different from other forms of discrimination insofar as your employer is allowed to 'justify' age discrimination if it can produce genuine persuasive evidence to show that, although it is treating you differently because of your age, its actions are a proportionate (i.e. reasonable) way of meeting a legitimate aim.
It is often easier to challenge proposals at work that you think are age discriminatory if you act together as a group, through your union if one is recognised at your workplace.
Remember too that if your employer is a public body, such as a local authority, or a private or voluntary sector employer carrying out public functions (which includes functions outsourced by NHS Trusts or local authorities), it must comply with the public sector equality duty. The duty requires employers to have ‘due regard’ to the need to eliminate discrimination and to advance equality of opportunity and foster good relations when carrying out their powers.
It can be worth reminding your employer of the importance of the duty, to support your case against the introduction of potentially discriminatory change.
You can find out more about the public sector equality duty on the website of the Equality and Human Rights Commission.