Do u advise to stay in a family if I'm going for about 2 weeks in London?Is it less expensive?

I wouldn't recommend it...not if you are going for two weeks, because you wouldn't have that much freedom, and that's part of the experience !. I would rent a cheap flat, stay in a Bed and Breakfast, or a hostel, where you would get to meet lots of interesting people !

Central London can be real expensive, even the cheapest hotels are quite expensive.

It is a good idea to stay with a family

For transport, get a weekly transport pass twice to move around.

Good luck for you trip!!

If you stay out of central london you should be able to find cheap accomadation without the need to stay with a family, london is a metropolitan area so regardless of where you stay it will be easy to get around cheaply.

I don't know about London, but when I go to Ireland I always stay with family. It will get very expensive.

No, get a b&b, its just as cheap with more freedom and there are loads in the city.