Was doing a little bit of research on the web tonight and found this really useful site for Cumbria, very similar to RCAHMS for Scotland, perhaps not as detailed, but still very useful. You can check the map, look at the area you want to search, either decide to look for sites according to age details, Prehistoric, Neolithic, Iron Age etc..zoom to the marked areas on the map and click on the information to check the details for the site.