"...the person or body who..." vs. "...the person or body which..."

...request the person or body which has the responsibility... ...the person or body to which the application was directed...

Both forms are in regular use. In the example given either would be acceptable, and even referring to a body alone "who" is often used, but probably not in formal usage.

The vagueness over this issue can be illustrated as follows:

In English law there is not necessarily a clear-cut distinction between natural persons and bodies. Some bodies, such as certain professional partnerships, comprise a group of natural persons, and there are natural persons who in legal terms are corporations.

It used to be considered correct form to begin a letter to a company: "Gentlemen,..."

There is a related question as to whether a body should be referred to as "it" or "they". In some circumstances "it" will appear odd; in others "they". Sometimes the fact that what in legal terms is a person is over-ridden by the reality that it is composed of and directed by human beings.