Hi Tony - Are you sure that the name Sodum came from the Forest of Dean? My husband's 2x Gt Grandfather (Edward Howells) was born in English Bicknor. On 1861 Census he was living in a place called Gomorrah, which was an area nicknamed after the Bible's Sodom & Gomorrah. We have since found out that the area he lived was actually Pontlottyn, S. Wales. (near Rhymney). Hope this information might help you.
Regards Anne Martin