My husband will be applying for his family visit visa to the uk at the end of September. When he books an appointment can he get any date and does he have to make the appointment a long time in advance. The reason why I am asking is that we don't live in bangkok so we will need to fly. There is currently a sale on with air asia and we would like to take advantage of this. At the same time I don't want to book a ticket and then vfs have no appointments on that day.

Making a appointment with vfs you have to stipulate 3 seperate days of your intended visit,naturally if the time getting there due to distance involved ask for a later appointment time,

Hope this helps. 

It's a total pain. We live in Hat Yai and had the same problem, on the VFS Global site you can only book a week in advance.

Only a week in advance that's gonna be a real pain. Really wanted to take advantage of the air asia promo, but without knowing if vfs will have an appointment for me on that day it is a bit worrying for me. So not sure whether just to risk it or not. When you did book it a week advance could you get any day you wanted? Or were some days just not available?

Yes, but the available options were only Wednesday, Thursday or Friday. That was on the Monday morning so we opted for Thursday morning and booked flights for Wednesday afternoon. Fortunately from Hat Yai we've a choice of four airlines so getting a flight wasn't going to be a problem but so close to the date you won't get a promo fare.