End of September events
It's almost the end of September, but there are still a lot going on in London town. Anyways, September and October are the busiest social times in the winter calendar. You can still catch some events happening in the Totally Thames festival, until 30th of September. Everything that has to do with the Thames river. From archaeological walks to exhibitions along the Thames. http://totallythames.org
There is also this Friday the 25th September late night for some London museums like Royal Academy, Natural History Museum and Victoria & Albert, open until 10pm approximately, and full of events, new expos, drinks and snacks.
For example, in the Natural History Museum you will have the chance to speak to experts, handle and see specimens close by, learn about prehistoric cannibals and there are a lot of interesting events for kids as well. See more here http://www.nhm.ac.uk/visit/whats-on/day.html?date=25.09.2015 .
In Victoria & Albert there is design week. There going to be speeches by designers, exhibitions and performances. Find more here http://www.vam.ac.uk/content/exhibitions/london-design-festival-at-the-v-and-a-2015/ldf-late-night-at-the-v-and-a/ .
In Royal Academy you can discover the new exhibitions: Ai Weiwei (just started 19th of September), the iconic big Chinese modern artist, and Wanderlust by Joseph Cornell (which closes 27 of September and is in its final days). https://www.royalacademy.org.uk/exhibitions-and-events
Finally, it is Design week in London until the end of September. That means lots of art exhibitions and design events going on in London, plus the annual famous design expos: LAPADA (Berkeley Square)- London Antiques and Art Fair, 100% Design (Olympia London)- only open to the public on Saturday, Homebuilding and Renovating Show (Excel London), Tent London and Superbrands (Old Truman Brewery), PAD London (Berkeley Square)- Art and Design in 14-18 October.