I don't think anyone's denying it, but once the plastering is done, that's pretty much it other than the odd trip to the wholesalers.
A spark will have to submit a notification via their CPS afterwards, which is maybe an hour of paperwork per job, plus a half day on site assessment of 2 jobs once a year with minimal paperwork requirements.
A solar installer who's doing the MCS side of things will have minimum half a day of paperwork for every job they do, plus their CPS assesments once a year, plus their MCS assessment once a year that also involves an absolute mound of paperwork, taking 1 person maybe a week in total, plus all the other stuff previously discussed.
now, if the agency is going to take care of all that stuff and the spark just needs to show up, do the job, and go home and put his feet up, then maybe a £150 day rate could be viable if the work was regular 3-4 days a week. But that's not what was initially discussed.