Hi and welcome, Like you my surname does not have any Clan affiliation so my only recourse is to adopt the clan of my mothers surname or to wear a general or district tartan to which I have an affinity.
However as many will tell you, with just one or two exceptions you can wear whatever tartan you like although out of respect you should learn the history of the tartan and have a ready answer when questioned why you are wearing so and so tartan.

As Paul and Chas have stated above most people havent got a clue identifying different tartans and the Sobieski Stuarts Vestiarium Scoticum is treated with a certain amount of scepticism. Our own legend of the kilted world Hamish Bicknell has a collection of over 100 kilts and I am sure wears each one with pride and panache.

So wear whatever you feel comfortable with. Wear it with pride and a hearty welcome from an Anglo-Welsh man from the south of the uk.