No appointment dates available!!

Hello,
I guess this question could easily apply to any of the different tiers, but i am posting it here as i am applying for a student visa.
I finished my online application for a visa and i am at the stage of booking an appointment date for the interview and biometrics. However there are no available dates remaining from now all the way to october! My course starts september 19th, and therefore i need to get the visa before. This particular embassy(barbados) does not accept "walkins". So what options do i have?
I am of the opinion that i should keep checking and maybe something will become available, is my thinking correct? or once it is filled, that's it?? Please Advise,
Thanks