You don't need consultancy, consultancy needs you. As I have explained in my first article that you can self-apply to the universities, I’ll say you the drawbacks of applying through consultancies.

1. You won’t learn anything. Consultancy will do everything for you and you miss out on learning how to research, how to think about universities, you won’t know the merits and demerits of the university you are going. Just to be short, you’ll be spoonfed and you’d try to be spoonfed for the rest of your life.
2. Obviously, it’s gonna cost you more money compared to you doing it yourself.
3. Consultancy will send you to the common university which they have tied up with and those universities won’t be the optimum university for your profile (however good or bad it is).
4. After saying all these, I applied myself just because I was lazy to go to consultancies, lol.