Just because you can’t find this information does not mean it’s not true (as you are no doubt insinuating 😀).
Here’s an extract of a letter James Knox, Chief Executive of The Art Newspaper, wrote for The Scotsman in 2007 as just one example:
“The saving of Dumfries House in its entirety, as proposed by SAVE Britain’s Heritage, would, at a stroke, transform the economic and employment prospects for the town and district. It has become something of a cliche that art can transform peoples’ lives. But with Dumfries House, this is most emphatically true. Everything must now be done to save this unique work of art.”
www.artfund.org/blog/2007/05/21/why-dumfries-house-must-be-saved
And also here:
“With the announcement of the sale, preservationists lamented the imminent dispersal of an ensemble said to have remained virtually untouched since an 1803 inventory, and organised a campaign intending to buy the house and hold it in trust under the Save Britain's Heritage organisation…The estate was finally purchased as a whole after Prince Charles heard about the campaign from the writer and campaign member James Knox, who made "an impassioned impromptu speech" at one of the Prince's bi-annual conservation conferences at Holyrood House in Edinburgh”
www.wikiwand.com/en/Dumfries_House