Equipment Flying This Weekend IAD-LHR???

Greetings fellow Virgin Flyers... Sorry if this is the wrong place to post, but a colleague over on FlyerTalk suggested I post this for the guru's here... I'll be flying Virgin for my first time this weekend, lucky to use my CO miles for a UC seat. Flying IAD-LHR on Sat 8/18 #22, return on Sun 8/22 #55, and wondering what the equip for this flight is. I've checked the routing info on v-flyer.com and think it's gonna be a 343 but in calling Virgin, the CSR said a 744, which I believe is bogus. If anyone here could help me with some better info I'd appreciate it. Was hoping for a 346 with new suites, but guessing it's not to be.... Thanks!