Try the social services department (Fostering and Adoption section)in which you now live or where adopted. They should hold a file on your adoption and contained in that will be your father's details. They can also offer you counselling , because the reality can be quite traumatic.
You are entiltled to see the full file, unless there is something in there that would be harmful to your health.
Hope you find your father
To start you off, you could put an advert in the paper, where he lived asking for details of his whereabouts