Exit Seats/Extra Legroom Seats IAD-LHR 29th June

Hi,
I am flying IAD-LHR on June 29th. I want to buy an Exit seat as i am 6ft 5' tall. I did not book my flight through the Virgin Website so I know that I cannot pre-book an Exit seat over the phone.
My flight appears to be pretty full, so I am a little worried that the Exit seats may all be sold, even though I plan getting to IAD 3 hours early.
Is there any way of checking to see if the Exit seats are all taken? I know that they are always blocked out on the online seat map, but I was curious if any of you had any advice for me, or "insider knowledge".
This is only my second post, so I apologize if this is covered elsewhere on this wonderful site!
Thanks
JDM
I am flying IAD-LHR on June 29th. I want to buy an Exit seat as i am 6ft 5' tall. I did not book my flight through the Virgin Website so I know that I cannot pre-book an Exit seat over the phone.
My flight appears to be pretty full, so I am a little worried that the Exit seats may all be sold, even though I plan getting to IAD 3 hours early.
Is there any way of checking to see if the Exit seats are all taken? I know that they are always blocked out on the online seat map, but I was curious if any of you had any advice for me, or "insider knowledge".
This is only my second post, so I apologize if this is covered elsewhere on this wonderful site!
Thanks
JDM