This coming Friday evening (Oct 26) UK radio station Classic FM will broadcast a live concert of John Williams conducting his film music at the Royal Albert Hall in London. The concert is sold out. Start time is 7PM (UK time) and according to my schedule for that evening in the TV and Radio listings it looks like it will go until 10PM. You can get more information here on the CFM website. There is also a Listen button on the page but I don't know if that will work outside the UK.
Update - because of illness John Williams wil not be conducting tonight. The show will still be on air but Dirk Brosse will be conducting.