Can anyone tell me how many months are usually given to first time UK tourist?

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I'm planning to go on a holiday to the UK and stay with my partner for six months. However, this will be my first time to leave the country and although the UK immigration & visa website says that the maximum duration that you can stay in the UK is for 6 months if you have a visitor's visa, a friend told me that they just might let me stay for a month or two since this will be my first time to visit. We can nonetheless prove that we can afford to stay there without asking for public funds and I do intend to return after 6 months because of my daughter (I'm a single parent). Is there anyone in mylot who can give me any information? Many Thanks.