I have watched this several times since its first broadcast, now nearly a quarter century ago! You can still find the VHS tapes in local libraries, but this is becoming a rare thing. I seem to recall that it is now released as DVDs, but I could be wrong. Hunt this one down, in whatever form. It's fascinating from its opening scenes right through to the end. For me, as a history buff, it ranks in the top ten best documentary series ever made, right up there with Ken Burns and Richard Attenborough. No joke.
A quick note: there is a 2002 similarly named documentary series called "The *Adventure* of English". It is also a great series, but not as comprehensive nor as entertaining as "The Story of English".
I'm glad to have had the opportunity to finally post comments about this series. An oldie but very goodie.