Dave, the aigrette worn by Queen Alexandra in the painting discovered by Knightship
has nothing to do with the Girls of Great Britain and Ireland tiara, which is today worn by HM, QEII. The Girls of Great Britain and Ireland tiara was constructed as a wedding gift for Queen Mary in 1893. It was not even finished just before the wedding date and so, initially, a sketch of it was displayed with the other wedding gifts. The tiara was made by Garrard. The funds for it were raised by a public subscription throughout Britain and Ireland, and a committee of ladies oversaw the design etc.
The video you were thinking of involved Rolfe Harris (shudder!!) doing a painting of QEII.