Location, location, location

Well, after spending one week searching for a flat to rent in London town, I thought it'd be very convinient to explain what I've been through so you can avoid this situation if you ever think about comming to London as I did.
First thing you must know is what you probably already know, and that is LONDON IS VERY EXPENSIVE. The first time I came here in 2007 I stayed in fancy hotel room in Barbican, within an area called "The City", that's where the famouse Tomer of London is and of course the bank area and the Tower Bridge. Very central, very nice. But expensive. The second time, I stayed in a hostel room in Bloomsbury, Russel Square north part of central London near the British Museum, an even more expensive area but we could avoid paying a lot sharing the room with other 17 travelers. Wow, isn't it? Anyway, it was fun! we spent a great time there although I couldn't get into the beds, they were too small.
This time I decided to stay with a local family, which turned out to be the best option I could imagine. Why? Because you have the experience of living the English life, you can know the local experience, local food, etc. Besides, if you ever have a problem like I had, they'll tell all you need to know. For example, where's the nearest hospital and how to get there, which supermarkets are cheaper, how to buy a mobile phone, which neighbourhoods are better to avoid, etc. They're always a good sourse of local and practical information when you have been in London but not really lived in there.
On the other hand, staying with a family, although is cheaper than a hotel, it can't be teh definite option when you want to live in a city. So I went searching for a flat. Oh gosh!
Ok it's simple: if you want to live in Central London (zone 1), you must share, unless you are willing to pay at least £400pw (per week) a small one bedroom flat with kitchen and private bathroom in a decent location. Of course you have multiple options, you can always pay more! But if you share, you can find a comfortable bedroom in a decent flat for just £100pw, £170 if you go to Kensington, Nottin Hill, Hyde Park, etc. Bills included (very important).
If you don't wish to share and you want your own spot, you'll have to go far away from the city, to the London boroughs, (zones 2, 3, 4, 5, etc) where rent is cheaper, but you're far away from downtown. There you can expect to pay £170, £200 or £300 pw for a one-bedroom flat or even a studio (sigle room sometimes with a kitchennet built in and a toilet, shared or private depending on the price). But if you do move to one of these areas, is always good to visit them first and find out with local people if they're safe or not. For example, I've told East London is not so pretty as the West. Some areas of the North are more dangerous than others in the South, etc.
My personal experience tells me that is always good to be near a tube station, so keep that in mind.
When I look for a flat, I always make sure I'd be near a tube station, then I look in the map that station and that's how you can see how well conected that place is. The postcode is useful too, but you have to know it well. The first letters in the postcode indicate the area you are in, S (south), NW (north-west), etc. and a number that basically tells you how far you're from downtown. For example my postcode now is NW2.
The rest of the postcode are another number and two more letters, which I haven't deduced yet.