Duram Roof Paint peels off after 6 weeks.

We recently painted our roof with Duram Cooltech Roofcote. This is their flagship roof paint. We were told that it is good paint. We usually use Plascon or Dulux. We removed old rust and paint with a steel brush, replaced some of the roof sheeting, app**** acrylic undercoat and then proceeded to paint the roof. Al was well till about 6 weeks later when the paint started peeling off EVERYWHERE! Even on the new roof sheets! The are paint pieces everywhere inn our garden and in our pool. Every time it rains there are more. By now half the paint is gone. Duram sent out a technician and we showed him our receipts. He did and inspection and told us that we didn't apply enough undercoat. And that was that. So save yourself a whole lot of trouble and just stick to Plascon or Dulux.