Hi all,
I've just stumbled across an excellent site for finding hi-resolution photos of probably several Welsh towns. I was searching for Chepstow dockyard, but the site appears to cover all of Wales. The Chepstow section alone has 60 photos, many are aerial photos, both from the early C20th and more recently. As always best to open this link in a new window or tab.
http://map.coflein.gov.uk/index.php?action=do_images&cache_name=&numlink=33167#...

From the above index I found this excellent shot of the old National Dockyards in March 1921, by clicking on a small index images it will enlarge into large high resolution photos like this one.
http://orapweb.rcahms.gov.uk/coflein/W/WPW006063.jpg

Here they are in 2009.
http://orapweb.rcahms.gov.uk/coflein/A/AP_2006_2284.jpg

Hope this helps with your researches across the border.

PS
Bit tricky to navigate for me as in Welsh language, I'm hoping I'll find an English version to post here. Meanwhile this appears to be the "search" box page. I entered "Monmouth". Yep, Wiki tells me that "chwilio" means search or find.
http://map.coflein.gov.uk/index.php?action=do_gazetteer&placename=monmouth&subm...