Help needed for visa

[Vale]

Hello, I hope someone can help me.

I am planning on sitting for an examination for obtaining equivalency of my degree next year (Late April and then June,as it is a 2 part test). As part of the preparation I am allowed to what is called "seeing practice" (which does not require any specific visa as it is not working, nor studying ). I have arranged some places to visit in the UK which would be for 6 months (September-February).

As a non-visa national I could go just as a General Visitor for those 6 months. But, what can I do in order to stay afterwards until the date of the test? I am planning on taking maybe 2 short preparation courses (that last 2-3 days) in March and April. I believe a Student Visitor visa would be needed for those courses, but I think that would still count as visitor. Is it possible to do that? What other options do I have?

I would appreciate your help, thank you, and sorry for the length of my story!