In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Henllys like this:
HENLLIS, a parish in Newport district, Monmouth; on a branch of the river Usk, near the Crumlin canal and the western Valleys railway, 1½ mile N NE of Tydeo r. station, and 3½ NW of Newport. Post town, Newport, Monmouth. Acres, 2, 622. Real property, £1, 647. Pop., 238. Houses, 50. The property is divided among a few. The living is a vicarage in the diocese of Llandaff. Value, £40. Patron, the Vicar of Bassaleg.
GB Historical GIS / University of Portsmouth, History of Henllys, in Torfaen and Monmouthshire | Map and description, A Vision of Britain through Time.
Date accessed: 26th March 2017
Click here for more detailed advice on finding places within A Vision of Britain through Time , and maybe some references to other places called " Henllys ".