Shame this is the last leg of you're journey, as much as love the LDN, it is shit-expensive and i'm guessing after three months of boogying you ain't gonna have too much kashmoney left!
Let's see what I can suggest for London moneysavers:
1. Food. Tesco (big supermarket chain) will tend to have a 'reduced' shelf/section (all the about-to-go-out-of-date sandwiches etc). Take the reduced stickers off of these and wack em on £10 sushi/whatever you feel like and get it for pennies. Yum.
2. Travel. Get good at 'doubling up' behing people through ticket barriers, travel on the Tube is a fucking rip off, even buying a weeks Travelcard/Bus Pass will still set you back a fair bit. Good answer to this is 'Chinese' travelcards...I'll save the details for a PM I think.
3. Getting pissed and dancing. If the cash situation is really getting low, but you still fancy having a pop at some High-grade English totty... No matter what sort of music/scene/pussy you're looking for we can cater to it. Plan B in Brixton does good hip-hop nights, smallish club but good. Throwdown on every 3rd Thursday of the month (i think) has a load of canvas graff/art on display, open mic, break battles and all that jazz. Worth checking out.
For all night stuff, try FabricLive up in Farringdon on Fridays>> good couple thousand people, hip-hop, drum and bass rooms, again DEFINITELY worth checking.
Can't think of any other nights to check out at the moment, but try and get drunk beforehand as drinks in the clubs will cane your money.
4. Narcotics. Not REALLY my thing so can't offer much advice.
Hope this drivel is helpful, i'm pretty drunk so will try add some more stuff tomorrow.
Have a good trip ya lucky cunt.:)