I think that the respondent has to wait a period of 3 months enforce they can apply for the Absolute ... Hope others know better, could it be that there is a cost associated with the Nisi £45? It was for my ex.
As respondent, you have to wait 3 months from the first date that the Petitioner can apply for the Decree Absolute. So that''s 6 weeks and 1 day plus 3 months.
The fee for a respondent to apply for the DA is £90 as the application is made ''on notice'' whereas the Petition can apply on paper which does not involve a court hearing therefore costs only £45.
It may be worthwhile writing to the petitioner indicating that if you have to make an application you will seek a costs order at the same time due to the financial strain that this will cause. It may give the petitioner the kick he requires to get the ball rolling.