Hi Jamie, speaking as a kilt wearing Scot, living in Scotland, there are few 'Tartan Police' going about and I haven't met one in over 50 years of kilt wearing.
If you're really wanting to go by the book then you could write to the Clan Chief of the clan to which you feel the closest family link, if there is no present Chief then the Clan Association should there be one, asking permission to 'officially' wear the tartan. This is what I did as the original name was lost through marriage.
Or, you could just give the traditional answer of, "It was my grannie's tartan", the advice given to me by my first kiltmaker, the late Jimmie Kilpatrick of Luss.
Please enjoy wearing your final choice.


Bring Forrit the Tartan