What a catch; fantastic considering that Historic Scotland "de-scheduled" the stone in January 1999.
Besides some farmers and horses, Brian was the first after Coles in 1898, to actually "see" the stone.
And what to think of the "bonus" one? Great!
There are some more decorated stones cemented into walls:

Glengap: http://rockartuk.net/c986014.html
High Balyett: http://rockartuk.net/c399827.html
Barholm: http://rockartuk.net/c569154.html
Arngask Old Church Yard: http://rockartuk.net/c914157.html
House of Elrig: http://rockartuk.net/c1218913.html

Thanks for the link to the Houxty Cottage, Rich!

And yes, Pebble, I think about a "Cemented into Walls" collection on BRAC.

Cheers,

Jan