Q. A tower I have rung in has been either: been totally removed or has been replaced with a completely new set of bells. How do I represent this?

A. There is a special field to handle this: Removed Towers.

Edit your tower and set this check box. Then if this tower has a completely new ring of bells, ie not an augumentation, we recommend you add it as a completely new tower and to distinguish them we also recommend that you then change the name of the original tower slightly to indicate that it is the old bells.
Then, you can link the two towers together:

It doesnt matter which tower you link to which, or if you have three towers how you link them together. After this, you can in some stastic windows, combine tower stats together. for example:

Updates from Dove

Towers with the "withdrawn" flag set, do not have anything more than the location updated when Dove data is imported.