is it necessary to go through consultancy for UK as a student?

I think you friend is right. I did not use any agency and I did all the necessary documents I needed for the Visa to the UK. From my experience I don’t think it will take so much time to do it. A couple of years ago I really talked an agency about the visa applications. The process was so complicated and the cost was so high. From what they told me I felt they can not help me, in opposite they made my work harder and I had to pay high cost for the extra money that should not exit if I do it myself. I think preparation of the documents is a good practice for you to have idea about the UK business style. It’s a good chance for you to learn resolving problem by yourself. Not to mention you will save a big money.