Academic exchange from Brazil to London...is it worth it??!!

Hello!!

I am from Brazil, I speak english fluently and am somewhat familiar with the UK as my mother has spent years there working back in her early days and made several friends and long term connections.

Because of her work today and the connections she has, I'll be able to make a trip and have accommodations aswell as food without having to pay for them. As I'll stay where I was offered. That would also, be in London. However I am nothing more than a scared teenager and have not gone international alone like that plus am considered pretty socially awkward and fairly odd by the people surrounding me - I can't even order a McDonald's without having the cashier laugh at me. Seriously.

So my question, is it worth it to be in London for those few months? People generally say others are rude, is that true? Is it too cold? Do you have any complaints? Any tips? Any advice, whatsoever? Bout money? Bout locations, the subway, anythin at all? I'm worried about maybe, London being too big, too expensive, what if I have to live on the streets? F'course not, I'll have accommodations, but even then! So many things to worry about!!!! Help! Thanks in advance.