This may be a bit late, but of all of the suggestions, Liswerry and Woolos are the stand-outs to me. Local, fit in with the Cardiff/Newport feel, but aren't really based upon real places.
But just to throw my hat into the ring - perhaps you could call it "Pilloo Junction" (portmanteau Pillgwenlly & Waterloo juncts.)
Or "iard y wych tywysog cymru" ( for a proper Welsh feel)? [translates to "the Great Price of Wales Yard"]. Only problem is, with the lack of Welsh language use around a lot of S. Wales, especially Newport and Cardiff, it's probably unlikely to have ever been called a Welsh name. Up north, I could believe it a little more!
My last suggestion - what about Wentloog North? The area you're modelling is to the north(east) of Wentloog, there's nothing else / similar there (well, except the Freightliner terminal...) and it's a nice-sounding, interesting word...!
Hope I'm not too un-helpful!
Andy
P.S. Leon - the work you've done recently is stunning, still keeping your high standards, and it's coming across in the pictures. I'll continue to watch!