If you live in Canada (or other Commonwealth countries), you may be elgible to apply for a UK Ancestry pass. This permit allows one to work in the United Kingdom without a visa or work permit for up to 4 years if one of your parents or grandparents were born there.

The paperwork requires basic bank statements of self-sustenance, full length birth certificate, and the original or notorised copy of the relatives birth certificate you plan to use.