I personally think this is the best Sumatran tiger exhibit in the UK. The foliage in the enclosure is very well camouflaged, viewing is very good, off-show viewing in the house. I also think the viewing for the public is good for any weather with the raised walkway. I do hope Bawa and Surya breed, the exhibit has two areas so if Surya has cubs then Bawa can still be on show, Flamingoland apparently bred them in the 70's is this true [By the way it was Amur's they bred not Sumatrans].
F L did breed Tigers in the 1970s. If they were any subspecies they would have been Indian (probably usually called Bengal then), they could have been "zoo" Tigers though. "The Animals of Flamingo Land" (1976) just calls them "Tigers" "Panthera tigris". I have a photograph of my mother patting a young Tiger being walked around the park on a lead in the mid 1970s.
Yes, they were most common subspecies, but in 1990 they were banned from International Tiger Studbook, because all bengal tigers in Europe weren't pure-bred.