The challenge of getting "the best" family law barrister- recommendation needed?

For every divorce/separation, each party will need to swear an affidavit of welfare and affidavit of means. These will effectively determine who gets what share of the family assets and any maintenance. As a rule of thumb:
I would be very cautious about talking about rules of thumb in this context. What happens depends very much on the specifics of the couple's situation and how negotiations go. It's very difficult and potentially misleading to generalise.