Can you assist me with these two quick questions:
1. How do you determine the relevant external parties within capture too much and their interest (is this directly to the company)?
2. As it relates to the BIA was are the critical focus of that evaluation?
1.- To determine interested parties you need to ask your top executives, and/or heads of departments about who is important for the business, taking into account that an interested party can be an employee, owners of the business, regulators, clients, etc. To determine their interests you can also ask to each top executives and/or heads of departments, and yes, this is directly to the company. This article can be interesting for you How to identify interested parties according to ISO 27001 and ISO 22301 : https://advisera.com/27001academy/knowledgebase/how-to-identify-interested-parties-according-to-iso-27001-and-iso-22301//
2.- I am not sure if I have understood your question, but during the BIA basically you need to collecting information from the responsible persons of each activity (some information: impact assessment, assessment of RPO/Maximum Data Loss, Minimum Business Continuity Objectives, etc), after this, with all information acquired you need to make decisions. I think that this article can be very interesting for you How to implement business impact analysis (BIA) according to ISO 22301 : https://advisera.com/27001academy/knowledgebase/how-to-implement-business-impact-analysis-bia-according-to-iso-22301/
By the way, for the collection of information you can use our questionnaire (you can see a free version clicking on Free Demo tab) Business Impact Analysis Questionnaire : https://advisera.com/27001academy/documentation/business-impact-analysis-questionnaire/
You can also download our "ISO 22301 Business Impact Analysis Toolkit" : https://advisera.com/27001academy/iso22301-business-impact-analysis-documentation-toolkit/
You can download a free demo of this toolkit, and you can find the questionnaire template in the folder "Business_Impact_Analysis_Toolkit_Preview_EN".