Where a company is a member of a group and the business of any other company which is a member of the group falls within section 105(3) above, then, unless either—
that business also falls within section 105(4), or
that business consists wholly or mainly in the holding of land or buildings wholly or mainly occupied by members of the group whose business either does not fall within section 105(3) or falls within both section 105(3) and section 105(4),
the value of shares in or securities of the company shall be taken for the purposes of this Chapter to be what it would be if that other company were not a member of the group.