There are between 1500 and 2000 external governors on the governing bodies of universities and colleges, and with most serving two periods of office this means that there are approximately 250 vacancies to be filled every year. In any one year each institution is likely to fill 2 or 3 positions.
To find out how vacancies are filled and if new governors are being sought, prospective governors should generally contact the clerk or secretary of the institution in which they are interested. The contact details for the clerk or secretary are almost always provided on the institution's web site.
Many institutions advertise governor vacancies in the national or local press.