This is too complicated for a simple response! The NALC and SLCC published a joint agreement in 2004, which is still used today to evaluate Clerk remuneration from a basic list of responsibilities. This places the role on a ladder of salary points, within a small grouping known as a substantive range, which is coverted to pounds, shillings and pence using the agreed payscales that are published annually. Incidentally, SCP19-24 isn't a substantive range on either the old or the new payscales.
As your Clerk appears to have done her homework, (probably using the documents I have referred to), perhaps you could ask her to provide everybody with a copy of these items to help you all to understand the decision you are about to make? I've sent you a private message.