You should start by getting your father's birth certificate which will give his parent's names.

You can get this from the Registrar in Douglas, see
http://www.gov.im/registries/general/civilregistry/welcome.xml

Unless you have the exact year there is a search charge.
You can get the year by searching the index. This is available on microfilm through any LDS FHS.
Maybe some kind person on the Island would look up the index for you.