I have the same question. I'll be flying in Upper Class and I currently do not have plans to fly any of the Virgin airlines after. I'm Premier Platinum on United but am ditching them just this once for JFK-LHR due to United's dismal product, schedule, and service.
Any thoughts on where to credit? If credited to VS, am I correct in thinking that I could use the 12,xxx miles to go somewhere one-way on Virgin America?