I didn't have any trouble booking V&A but we were there in late Sept. when crowds were low. Also, when I called I asked for any night the week we were there (I did call 60 or 90 or whatever # is right, days out, minus about a week because I spaced!). We got a Tuesday, which was fine. I would recommend going early in your visit when you haven't reach the point where you feel like you never want another meal!
NB