As a 19 year old female you should be fine almost everywhere. In central London you should be able to hail a black cab through the night. Night buses run after midnight from Trafalgar Square to all areas of London. Check out our Travel Resources pages for more info on transport in London. There are several reasons to that.
Club nights can be regular on a weekly, monthly or fortnightly basis.
The two clubs nights that you are looking at may be alternating.