Thankyou for the reply. Its often hard to get information anout overseas ancestors when you in Australia, although the internet is wonderful now.
I am sure the Bryden family you mention is mine. All I have on Walter Bryden is that he married Margaret Greive in 1756 at Ettrick, Sellkirk and that he was a farmer. His daughter Christian is my direct branch, (which links in with Walters mothers name as you mentioned). I will look into this further. Thanks again.