I am a british muslim citizen I am married in pakistan so I live here with my husband and his family I have no privacy and always have to the take the permission of my mother in law or father in law to go out to buy things that are necessary for me my husband is lokking for a job however I am a working women myself islamically who am I suppose to get permission from when I need to go out to buy my necessary things and is it in islam to live with your in laws

You obey your husband. That`s all. There is nothing Haraam with living with your husbands family, as they are your maHram, but his brother is not, so you`d not be allowed to be alone with him, or take of your hijab etc.in his presence. You didn`t specify which members of family you are referring to. If it`s just his parents, then it`s Sunnah in my understanding that a husband provides for privacy and an own apartment for any and all of his wife's. When a girl marries, they move away from their fathers, and they come under their husbands. Then howcome the husbands parents are there in stead? I can understand the dilemma, and I don`t whish to come in between you and your husband or be a reason of marital discord. I repeat: it is upon you to obey your husband, respect him and his decisions, and help him.
You can discuss the matter gently with him. It`s understandable if he wants someone to look after you when he`s out. It`s a beautiful gesture. And they probably see you almost as their own daughter. Don`t think of it as oppression. Ask Allaah for Him to ease your worries, and guide your affairs, and after that cunsult your husband with kind words concerning how you feel. It`s not a question of Haraam or waajib. Islam is not black and white, or extreme, or a religion of conflict. Everything is balanced. There is mustaHab, there is manduub, there is makrooh in between, so not everything is either waajib or Haraam. The `amr` is in the hand of your husband. What he decides, then it is upon you to follow him in all cases, except if he were to order you to disobey Allaah - a`uuthu Billaah. And it isn`t easy for a woman to humble herself constantly especially in a western society, but there is great reward.
The evidence is that Allaahs Messenger -sAaws- said in the well-known Hadiith often mentioned by the scholars of ahl As-Sunnah wa Al-Jamaaàh that: "A believing woman who prayes her salaah, fasts her month, protects her chastity (private parts, from illegal sexual intercourse), and oneys her husband, then she will be allowed to enter Al-Jannah through whichever of it`s eight gates she whishes.", or the like of that is what he said -sAaws.
If your husband gives you permission to leave your house without seeking permission from his parents, then that is fine, and hopefully they accept, because Islamically they have no authority over you, but you must respect them as we all must as muslims respect our elders, but your obedience is to your own parents and not to them, but first of all to 1. Allaah, 2. His Messenger -sAaws, and 3. your amiir, which is your husband.

Excuse me, please. By: "oneys her husband", I meant: "obeys". And Allaahs Messenger -sAaws- said specifically "Laa taa`at al-makhluuq fii ma`siyat Al-Khaaliq." - "No obediance to a created one in disobediance to The Creator." So remember that this world is only a trial, and little are it`s enjoyments for a while, but who is constant upon worshiping Allaah Alone, and making Religion sincere to Him, they should have patience with what Allaah has given them, and be thankfull, and work for the Paradise of the Aakhirah, because the paradise of dunjaa is nothing but illusion.
And be careful also that you don`t come in between your husband and his parents, because causing separation between them would be a sin - by separation I mean that they weren`t pleased with him, or that he would in some way dishonour them -a`uuthu Billaah. As far as searching for a private accommodation for you, then it would be your husbands duty, but as he is unemployed, so make Sabr.

As for the evidence for his brother being non-maHram, you can see:
http://www.questionsonislam.com/index.php?s=show_qna&id=1181
His cousins are also non-maHram to you naturally, as are your own cousins too.