London is a great city, but expensive. Except for the beer and ale!
Take the tube. Much faster and less expensive than taxis. Just take a couple minutes when you enter the underground to get your bearings.
Most pubs close at 11:00 as has been posted.
If you want sex check out
Punter Net and go to one of the "parties". Typical is three girls over three hours for 120 pounds.
Visit Soho (just beside Piccadilly station) to check out the sleeze. Great bookshops as well. Short fast sex with lovely young women can be had for 30 pounds. Look for the "model" signs in the open doorways.
*Do not* go for the "Private Shows". They will roll you for 100-200 pounds.
Have fun!