Sue
I don't know if it is any help but ... there are often several spellings for the "anglisized" name we are researcing eg Kerr is also known as : Ayre, Evers, Hare, Hever, McGirr, Orr, Ivor, Ycord etc.
It may be worth while finding out what other varaiations there are of the name in question
Best of luck
Terry.