A controversial post from Stu.
In general, I think the Knox-Robinson view of church is right, and builds on a pretty standard Protestant theology of the Universal and Local Church. It adds greater biblical and theological and in fact biblical-theological clarity to these earlier formulations.
But I agree that the church-as-gathering theology needs some qualifiers. For one, I reckon 'a local church is not A church but THE church' is one of the most unclear ways of making a point in the universe.
Whenever we make too big a fuss about 'using words properly', it's important to acknowledge, as Stu does, that different languages have different ranges of meanings... and so English 'church' can mean building and so forth.... Although he seems to make the opposite point in this post!
Also, saying 'church doesn't have a mission, it is the end goal' is not very clear. An end goal can also have subsidiary functions. In the case of the church, God doesn't gather to himself a people who get cryogenically frozen. He gathers to himself a people who are active in loving him and one another. Part of being the end goal is being active in serving God, his people and purposes.