Church and chapel data from The Religious census of 1851 : A Calendar of the returns relating to Wales, Vol 1, South Wales. Ed. by I.G Jones, & D. Williams. UWP, Cardiff, 1976. The names given towards the end of each entry are those of the informants. Check with Gwent RO to see what extant records are held, and possible names of chapels/churches built after 1851.
Treleck Grange Chapelry; Statistics; Area 1774 acres; Population 85 males, 63 females, total 148
Treleck Grange Church Attendance - (average) morning 20/30, afternoon 20/30 (alternate?) "......The few cottagers of Treleck Grange may send their children to Tintern National School consequently they are expected to attend there on Sundays" 1 service in English Henry Warrilow, Incumbent Minister
Family Search have an interactive map called "England and Wales Jurisdictions 1851" showing parish (and other) boundaries with optional background maps such as Ordnance Survey. There is also a Search facility, do read the guidance notes to get maximum benefit from this useful resource. See here for further background information to assist in the interpretation of this data
Kain, R.J.P., Oliver, R.R., Historic Parishes of England and Wales: an Electronic Map of Boundaries before 1850 with a Gazetteer and Metadata [computer file]. Colchester, Essex: History Data Service, UK Data Archive [distributor], 17 May 2001. SN: 4348. Here is a gazetteer/finding aid plus a set of overview maps to accurately identify the position of parishes within the county.
You can see maps centred on OS grid reference SO492106 (Lat/Lon: 51.791734, -2.737952), Trelleck Grange which are provided by: