Unfortunately divorce and finances become messy if one party becomes demanding and in your words "outrageous and astonishing". Sadly when one party reaches that state of mind mediation (not arbitration) will probably be a waste of time.
It looks like court beckons. One will be the pursuer and the other the defender depending on who gets their writ lodged first. Thereafter pleadings (both sides of the story) will be recorded and put before a sheriff to determine the final outcome. The quickest and least expensive way to finalise matters in court is by way of a ''joint minute'' but only if both parties can reach an agreement.
Otherwise divorce can be expensive and the only winners are the lawyers and their accountants.
There is a cliche that there is nothing lawyers like more than a client who says it is about principle because they will fight to the bitter end no matter what the cost.
Being asked to put a figure on the costs of going to court is rather like being asked how long is a piece of string. IT all depends on the work involved but to go through to the bitter end typically costs £12k+. One poster and his wife spent £100k between them on legal fees for assets worth £250K and they didn''t even get to the end of court proceedings.
A lot of the cost involved comes about due to the fundamental lack of agreement over ''facts''. Each party will have a different version of events and each person has their own recollection of those events.
If you can''t agree on what actually occurred, the chance of reaching a compromise is slim. Letters and statements dealing with each of the parties'' version of events documents the position of each party which is then put before the court to decide on what is fair and just - which can involve a judge choosing to prefer a particular version of events.
In order to adequately summarise the position of a party, there is a lot of background that has to be addressed and a considerable amount of time has to be devoted to the background in order to present a case fully. It is not just about the here and now.
A seemingly trivial task suddenly presents a completely different set of challenges. As an example, describe a television set. You can probably do that in a couple of sentences. Now, describe a television set to a person who has somehow travelled forward in time 200 years. How much detail do you to go into in order to make that person understand exactly what the television is, what it does and how it does it?
This doesn''t answer your question but be sure of this, each party has in their mind a version of events. How far apart those are from reality will determine how much each party could spend in reaching a settlement or obtaining a settlement imposed by the court. The closer the parties are to reality, the more likely it is that a compromise will be reached without going to a final hearing.
As I have said before on this forum, nobody will be entirely happy going to a final hearing and if your have to forego an extra £10k to avoid this step that''s what you should do. It will cost you that much just for the preparation and attendance at the final hearing and the stress involved is considerable.
Apart from the costs of solicitors'' letters, phone calls etc there are significant costs in preparation for court and the solicitors'' fees for attending court. At the first hearing the sheriff will decide how to proceed and set a timetable for future hearings.
There may be several procedural and option hearings before the "proof" hearing where the sheriff determines a settlement. Most cases are settled through solicitors haggling in court corridors.