Mixed drinks are £2.75 ish in a pub, and when I go to clubs I drink beforehand so I dont know what they cost there.
Best kept secret- flights to France and A-Dam are actually a good deal cheaper than eurostar, if you buy at the right time you can get return flights to Paris on easyjet (ryanair doesnt service paris) for around 35-40 quid, whereas a 1 way on eurostar will run you about that much or more. I was going to go last week but they jacked the prices up to about £140 one way. They do that often. I'm going to Roma next week, I paid £30 for my return, including traveller's insurance. The thing about travelling around in the summer is that it'll be more of a pain in the ass and more expensive.
I live in London right now and have been up to scotland for a few days (take the train, get a young person's rail card for £20 and use the hell out of it) and went to Bath and Cotswolds. I would highly recommend getting out of London (you'll want out anyway for a bit every now and then) and seeing the rest of the UK. Just the few places I've been are really incredible, Bath was gorgeous and had some really sweet shopping. Three days is plenty for trips, when I go out somewhere I usually have an afternoon/evening off and a day and thats alright. Not incredible, wish I had more time, but doable and gives me a taste.
horrifically expensive (especially if you're operating on dollars ouch), however if you take care you really dont have to spend that much money. For example, make yourself take the bus instead of the Tube generally. You see where you're going, and its only £1.2 for a single or £3 for a day pass as opposed to £2 and £4.7 on the tube. Besides its quite thrilling to sit just above the driver, you get this disgusting sensation that death is right around the corner, literally. Shop at supermarkets, cook for yourself (and compadres) and in the summer buy fruit at the ubiquitous outdoor markets. I find that I can eat well and eat healthily easily on £2 a day, not including a bottle of wine if I feel like it. I've also managed to find some really good cheap cheap restaurants.. Trial and error. As I mentioned before, drink before you go out. My friends and I play drinking games for an hour or two before we head out, otherwise you'll wake up the next day with a completely empty wallet.
If you have any specific questions, I'd be thrilled to help you out.