How can I use a class variable with many possible values in logistic regression?
This may not be the answer you are looking for, but I think this is a telling part of your challenge


  My hypothesis is that the propensity to say 'no' will be stronger in some individual respondents than others, be it for psychological or geographical reasons, and that these individual differences will be a stronger determiner for the dependent variable than any other class variable.


Unless I misunderstood you, it seems you want to have an input parameter that indicates how reflexively a respondent will be to just respond with 'No'.  The problem is, as I see it, you don't know the answer to this.  You have no way to measure this directly.  No? 

If you have more data about the respondents, maybe you can back into this.  Huge assumption here, but if you could get a count of the number of recommendations made vs the number of times they have said 'No' you could come up with some factor:
$$f_{(No)} = {{Number\ of\ "No"\ Responses}\over{Number\ of\ Recommendations}}$$

This may get you what you are looking for, but it assumes you can tie back the data to the respondent and that the respondent is, in fact, the Branch Manger or Sales Representative, not the customer.  The problem with this approach is that it assumes that all the recommendations were equally competitive.

HTH