Due for an eye test, best way pf doing it?

Currently living in tokyo and recently got my reminder from by UK opticians that I'm due for an eye test.

I found alot of information pointing towards just going to a glasses store and getting their free test, but am wondering if that's it? I've also seen alot of eye clinics coming up too. At home id pay about £25 for a test to check everything about my glasses perscription and look over my retina ect. Is all this covered in the free test or do it need an eye clinic?

Also, how much does all this cost?

Fyi: daily glasses wearer and haven't noticed any vision changes but like to stay on top of things

Thanks for any advice:)