It's best to wait for the confirmation of your appointment slot first before paying the visa fee to be on the safe side ate, that's what I did. As what smileyangel suggested, you can walk in but you have to be early as they only accept walk in applicants from 7-8am. Even if you have booked VIP premium appointment that day and you arrive earlier you can always join the walk in applicants and ignore the VIP appointment, It doesn't matter. You should get the confirmation from them shortly unless they are very busy.
