Tom, a few years ago I did the same thing to my Mercian. I was going downhill having just finished the climb and went from my large sprocket to my small sprocket in one shift--oops. the chain wedged itself between the freewheel and dropout causing the wheel to lock. My frame was repaired by Leonard Zinn's crew and even though the dropouts were a discontinued style he was able to find a replacement. The right rear dropout was replaced and the entire frame was sent to Rainbow Cyclecraft for new paint. The total bill (with the correct decals) was around $500; much less than a new frame. The bike looked new when they were done.
Paul Patzkowsky Longmont, Colorado