Personally I'd put the holiday on hold until I got the BVB.
If the holiday has to go ahead then the safest route is to wait until after it to apply for the visa as there is no guarantee the BVB will be issued in time, although I'd say it's likely it would be.
If the holiday has to go ahead then the safest route is to wait until after it to apply for the visa as there is no guarantee the BVB will be issued in time, although I'd say it's likely it would be.