Well it's LONDON, so nearby bars and alcohol is almost redundant - they're everwhere ;) Until around 12 at least.
Then the pubs close, and the nightlife and bars and clubs continue in certain areas.
The obvious is Central London.
Plenty of hostels and hotels.
Lots of bars and clubs open late especially around the touristy Leceister Square area, and Old Street area.
Expats often prefer Clapham Common, and to a lesser extent, Wimbledon - as the crowd is younger and it's far less touristy (and therefore cheaper).
A lot of Kiwis, Aussies etc, but then London is basically pockets of expats anyway :)
travel.stackexchange.com/users/101/Mark Mayo
We all know that London is a city full of life and color
so it is needless to say that the city has an amazing night life as well.
The night life in London attracts people from all age groups starting from the young teenagers to the old all are fascinated by the night life of London.
There are plenty of bars and nightclubs in London such as Corsica Studios , EGG , The Den and Centro, Fabric ,THE ISLAND, 333 and many more.
I suggest you central London would be your best choice to stay and enjoy nightlife and hotel charge comparatively cheaper in central London.
travel.stackexchange.com/users/799/Julia Cruz
Budget:
yha.org.uk
- I've stayed at (several times):
St Paul's YHA in both dorms and single rooms.
The nicest I think owing to the location (fairly good for East London (e.g. for Hoxton, Bricklane, Bow, Dalston), a (night) bus trip away).
Cooked breakfast (was inclusive at the time)
Thameside in dorms.
OKish for getting to East London
(Rotherhithe station nearby).
From there a lovely walk along the Southbank in the morning taking in all the arts establishments, Tate, South Bank Centre.
The worst that can happen in dorms is someone snoring continuously.
Which occured to me about 1 out of every 5 times I stayed.
Not bad run really!
couchsurfers.com can connect you with Londoners
who have (possibly free) accomodation Further up the price scale but
more private, hotels: laterooms.com - still good value in some cases.
Again, I've used this service several times in West London, South Bank, Camden, Greenwich.
Finally, another good way to find out about the nightlife is to listen to London radio stations.
For example on iPhone/iPod/iPad and Android phones there is the TuneIn radio app which lists stations by region, including London.
Kiss, Choice FM and Rinse FM will suggest urban, electronica and dance venues and club venues.
Other stations will suggest rock venues for example.
These would be available via PC/Mac as well by visiting their respective websites.
Jazz FM heavily promotes venues in London and across the UK.
As a guess it also might be worthwhile visiting during the week - perhaps for a more authentic London crowd who can make such venues where as visitors perhaps less likely to.
But then locals like to go out at the weekend too I would think.
Consider the time of year visiting.
For example in the summer, festivals such as Lovebox have after parties, as will Notting Hill Carnival - some advertised as flyers others verbally.
travel.stackexchange.com/users/303/therobyouknow
Covent Garden could be a great option for you.
Its right in the heart of London and you will get the exact kind of crowd you are looking for.
Bars can be easily found around this place.
My personal favorite is Thai Square restaurant and bar.
Hope you have a good time.
travel.stackexchange.com/users/14138/user14138
There's two main areas in London that are known for their nightlife.
London's Westend and Shoreditch.
There are bars and clubs all over London, but places outside these areas are going to be a lot more local than bars in town.
The nearest station to the West End is Leicester Square.
However the West End is associated a lot with tourists.
Directly to the north of Leicester Square is Soho which is generally more local but still very buzzing on the weekend.
Shoreditch has many bars, particularity around Shoreditch High Street and Hoxton.
Shoreditch is seen more "hipster" than the West End.
Areas such as Dalston are seen as even more "hipster" than Shoreditch so plan accordingly.
One thing to remember is that if you stay in either of these areas is that they can be very noisy during the weekend, so it might be a good idea to find hotels just outside of these areas and walk in.
Or just stay out to 2am...
:)
In Central London public transport is excellent and taxis are plentiful.
Covent Garden isn't really known for clubbing / drinking.
Yes, there are bars and clubs here but the area is known more for the Arts (Opera House / Theatre) and its interesting shops rather than its clubs.
travel.stackexchange.com/users/6509/Josh B
It depends really on what you're looking for quality wise really.
If your travelling on a budget I would recommend Generator hostels.
Clean, tidy and really nice people.
They tend to keep things under control so no crazy parties in the hallways.
The Hostels are placed all over London.
Mid pricing you'd probably do well around the Kings Cross area in central London.
Typically you can get a room for around £75-£100 per night in decent dwellings.
Just don't expect mints on your pillow or room service.
High end stuff, well really the sky is the limit in London.
Some hotel rooms come into the thousands...
whilst others keep it in the hundreds.
If you do get a chance to explore the nightlife I would always recommend heading to Fabric, Ministry of Sound, Egg, Studio 338 and My favourite Boujis.
Usually I just use Cluboid.com for guestlist or tickets to these events.
travel.stackexchange.com/users/21888/Samantha
For those looking to travel to London and enjoy the nightlife, where would be the best area to stay? Requirements are nearby bars, alcohol and 20-something crowd all preferably within walking distance.
Where to stay for London nightlife?
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<accommodation><uk><london><culture><nightlife>
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travel.stackexchange.com/users/1030/GBa
London has bars and alcohol everywhere, especially in central London, but you can try touristy areas like Leceister Square and Old Street, the younger and less touristy Clapham Common or to a lesser extent Wimbledon, Covent Garden or Shoreditch. Generator hostels are good for travellers on a budget, while King's Cross is more mid-priced. There are plenty of bars and  nightclubs  such as Corsica Studios, EGG, The Den and Centro, Fabric, THE ISLAND, 333 and many more. There is no difficulty finding nightlife in London. Central London is full of bars and clubs as are some other areas, such as Shoreditch, Covent Garden and Clapham Common. If you are on a budget, Generator hostels are a good place to stay. For mid-price hotels, see the area around Kings Cross. 
There are lots of bars and clubs everywhere in London and many stay open late. Central London is an obvious place to stay. Other areas include Clapham Common, Shoreditch and Covent Garden. Generator hostels are good for budget travellers and Kings Cross has good mid-price accommodation.