I'd say that Flight's fish is a silver bream - some pics of both silver bream and roach x bream in Big Roach 2 - it's easy to tell them apart with experience. I get the odd silver bream from Throop but years ago there were big shoals of them on the tidal Dorset Stour and I had a fair few a couple of years ago down there (also had one or two off the Royalty on the Avon which it adjoins). The Thames around Oxford has plenty and I've had them down as far as Wallingford and up at Newbridge. Other venues I've had plenty include the Trent just below Nottingham (Gunthorpe, Hazelford, Burton Joyce), the Nene at Orton, the match length of the Witham and a number of venues on the Bristol Avon from Staverton right down to Keynsham plus the Oxford Canal and some of the Ringwood gravel pits (long gone in this case!). They're often reported as 'hybrids' when nothing of the sort though you can also get silver bream hybrids (with roach, rudd and bronze bream).