Do not get confused by the name, [Student Agency]'s bus lines and other services are available for all customers, not only for students or youth. (In some cases, there are discounts for ISIC holders or young people of age <= 26, though.)
There is a possibility to buy bus tickets online; unfortunately, their e-shop is available in Czech language only. But the adventurous can follow this manual. :-)
The buses arrive at Grand Hotel Brno.
RECOMMENDATION: you may call 00420841101101 for reservations and information, they speak English.
You may also try info (at) studentagency.cz.