Does look a lot like a sun sign - similar to those in Scandinavia.
How many sun carvings are there in GB? The closest thing in the British Isles I know of are the examples at Dowth:
http://www.themodernantiquarian.com/post/4796
and Loughcrew:
http://www.megalithomania.com/show/site/47/177 (which is probably closer in design)