The Guardian has an article on the restoration of Wentworh Woodhouse.

".... So far, about 100 structural surveys have been carried out, more than 100 drains have been inspected, 110 tonnes of slate has been ordered for the roof, 200 tonnes of asphalt has been put on the new driveway, and 350 tonnes of rubbish has been removed from the site. It will take an estimated 15 to 20 years to fully restore the property. ..."

https://www.theguardian.com/culture/2018/dec/27/scale-and-splendour-volunteers-work-to-restore-wentworth-woodhouse