Just returned from a quick 7 night trip to London. Stayed at the Royal Court Apartments (not recommended). Went on a day trip to Stonehenge, Windsor and Bath with Gray Line Tours (recommended-very similar to Evan Evans Tours). Saw all the typical tourist stuff...Oyster Pass is very easy to buy and use. Highly recommended. Found that pretty much all the pubs are the same. No need to search high and low for a certain one.
Weather was great despite everyone saying it was so cold. I guess when it is -30 here it seems tropical to me! Did not notice a certain "dress code". You could wear anything and still fit in.
Food in London isn't as good as mainland Europe but I loved all the ethnic restaurants. It should be noted though that I am not a wealthy person who will easily spend lots of money on fancy meals...maybe they were good....and the best part was that it didn't rain for my entire trip except at night when I was asleep.
Didn't experience the nightlife as I was very sick of what I thought was a cold, but had bronchitis and and ear and throat infection...