Many of the rocks used for scaping like Seiryu, Manten, and Ryuoh are actually all types of limestone, so you could probably use them without any real issues.
They might raise TDS slightly but the frequent and substantial water changes that go hand in glove with eutrophic dosing methods will counter that to a great extent.
But more to the point...if you do try to take some home you might end up being prosecuted...Limestone pavements are of very high biodiversity importance in the Yorkshire Dales National Park, they are protected by Limestone Pavement Orders and continue to be on the UK and local list of priority habitats for biodiversity. I should image that there is similar protection for the Burden landscape...