If you are a fan of "The Clash" then you might get more from this fly-on-the-wall, partially dramatised, documentary that follows their ascendancy in the UK towards the end of the 1970s. To give it some sort of narrative, there's a fan inserted into the mix and he serves as a conduit to not just the story of the four piece's musical journey, but also to illustrate a Britain that was wallowing after many years of ineffective government, out of control trades unions, and on the cusp of electing Margaret Thatcher (who does feature now and again telling us about the safety of old ladies walking…