the reason this job has been advertised for so long as you say is because of the number of men on the job.
There is 35 scaffolders on the job at the moment and another 10+ required now so the money cant be that bad as you say.
the other reason why this job keeps getting advertised is because there is not that many scaffolders in and around the milton keyes area as most are on the job so the need is to advertise further a field hence the advert.
And finaly as you put it that agencys need to stop shafting peeps in the arse hows that happening if by the end of the day 45 scaffolders are on the job for at least 6 months.
How many more jobs accross the board are carrying that many men at the moment.