Those markings have always been thought of as Neolithic , I think Skara Brae would have been under sand when the rune carvers were around .The markings are very close to to motifs found on Grooved Ware .
Have you seen this stone Joanne ?http://www.themodernantiquarian.com/post/34422 .
Look familiar ?

Hi Kammer,

Wanted to mention that I enjoyed talking with you the other day.

Runes.
Just a small not +/-.
Stretch from 200bc to 1000ad?
There are two types, which seem more to differ by number of symbols than completely different.
There are also runes that fall out of this period and are somewhat strange to the runes we are familiar with, a Hungarian version that was dated much earlier 1000bc Historians don't know what to do with this either.

I find the geometric symbols on the stone more difficult to look at as 'letters' but it does look easier when one logs in with 'spacial conciousness' in mind (3 bloks in a row, which way up does the 4e go, thingy test)

Sorry if I take long to answer, one of the reasons why I don't participate much in longer conversations, ... I never went to school in the UK and have to think on every word