Benchmarking - Management and maintaince cost

I am revising financial appraisal model for new build and would like to benchmark key assumptions against other councils and private sector. Could someone provide cost they are using for their financial appraisals or guide me where I can find them. I am looking for following:

1. Management cost per property. £600
2. Maintenance cost per property. - £600
3. Majors works 0.8% of construction cost starts from year 11.

Thank you.