Thanks for the replies. I did a little searching on the Virgin website after posting yesterday and when I checked out the flight schedules, I noticed that they did indeed eliminate several of the later flights on certain days, both coming and going and they had switched my flights to the earlier ones on both my departure and return. I did receive an email from them this morning telling me that my original flights had been cancelled and they had rebooked me.

I guess I just assumed that 2 flights a day were always in operation between LAX and LHR.

I did book directly with Virgin.

Again, I appreciate your replies.