I did the OLCI course, the full one like you intend to do.
My experience was that the tutors at the centers are very good, all time served electricians willing to explain or discuss anything, ours even gave us his mobile number so we could call if we had a question.
I can't say the same for the course material, it was poor and in cases wrong (a shaver socket is not an example of SELV).
You will find you need to do a lot of studying on your own to obtain the theory side of the course, and I do mean a LOT.
In short, if you expect to take three years to do it, then go to your local collage, if you want to do it faster and have the money & time to study on your own, yes you can get the exams this way (it took me 10 months for the 2330).
Also remember that you can't get the 2357 without been employed in the trade, and don't believe what the salesman tells you about how they will find someone to employ you, it's not going to happen.
Only you can decide.