Yes, you're right again MPG,
John Simmonds' birthplace "New Weir" was indeed just south of Whitchurch on the Wye, not far from Lydbrook and more precisely and rather appropriately at Symonds Yat !. This was an important centre of industry many decades before John worked there.
http://www.overlookingthewye.org.uk/index.php/hidden-industry/new-weir-forge/

This Map shows the area, http://www.forest-of-dean.net/index.php/resources/15-maps/95-new-weir-symonds-yat-1890
Some general photos of the Yat area http://www.forest-of-dean.net/index.php/symonds-yat

More history ref the New Weir ironworks/forge here
http://www.historic-images.co.uk/herefordshire/symonds-yat

John's wife Anne was probably born at Marstow, just a mile or so north of Whitchurch.
http://www.genuki.org.uk/big/eng/HEF/Marstow/Gaz1868.html