If radial lines make a sun symbol, they're sun symbols, I reckon the lines would have to be outside the circle, to indicate rays. It's not a common motif from what I've seen/read. The closest thing up north is probably the tri-radial designs at weetwood cairn,
http://www.themodernantiquarian.com/post/9973
and Whitsunbank 2
http://www.themodernantiquarian.com/post/12443
But I don't reckon these would count as sun symbols, as the lines go through the circles, and three ain't enough for a sun, even up here.
the only other radial lines up here being a few at one end of a motif at Roughting Linn.
http://www.themodernantiquarian.com/post/11685
But I don't reckon these would count as sun symbols, as the lines don't go all the way round.
Apparently there's a little cup with radial lines, at poltalloch.
http://www.themodernantiquarian.com/site/2502
Which might qualify, but you can't see it on these pics.
And there's sorta flowery thing on Stanage barrow, but I couldn't find pics, so no link
Also the Ormaig rosettes,( v good pics now)
http://www.themodernantiquarian.com/post/29522
http://www.themodernantiquarian.com/post/18192
which might if you were stretching it, be interpreted as sun symbols.

Not that any of that is probably much help when you're talking about those freaky old sarsens.