I found these links recently regarding Islam, Muslims and Wales. The ww2talk.com link features some good historical photos of Cardiff's Muslim community:
ww2talk.com, The Germans bombed our Mosque-Butetown, Cardiff
Green Booked, Islam and Wales, 12 Oct 2010
Andrew Papworth's Blog, The importance of religion in Butetown, 17 Mar 2010 (contains a 1950s photo of Butetown Mosque)