International student in the UK

[Ssa11200]

Hello every body,
I am an international student (none-EU) in the uk. My study is funded by the university and my bursary covers my tuition fee and they pay me £480 per month for living expenses. Obviously £480 is so a little compared to actual living expenses in the uk. So, I saved some money and also borrowed some, altogether around £4000, to start a business.
I buy uk luxury brand products and supplements and post them abroad to my customers who are mostly my family, my friends, and friends of my friends. They pay the price of the products by local currency. To bring this money to the uk I either can use currency exchangers through bank transfer or get paid by cash through currency exchangers' partners in the uk. The second one is much easier as I can have my money immediately ( which is very important my money to be in circulation) and don't need to wait several days for my money to appear on my account.
So, I transfer money to exchanger's local account and get cash from their partners in the uk. Every month I need to put around £3000-4000 cash in my account. By this way I can earn up to £700 per month.
I am student and it is very important for met not to get into trouble financially. I am a little bit worried because I fund my account by cash. I was wondering if any of you could please help me and give me some advice?