I had similar with my Eclipse, the paint was wormed all over the frame as per the image. Shining a torch down the seat tube and it's junction with the top tube as well as the head tube and bottom bracket showed no rust at all that I could see, or at least nothing that didn't just wipe away. So I sent it off to Chris Marshall for a repaint. He confirmed that it was all just surface rust and the frame was good before respraying.
So...I reckon you are probably ok, but I did have the comfort of actually knowing that in the end.