Cheers. The reason for the silly price by the way was that the holiday company gets a big discount for regular economy but any upgrades are up to the commercial rate. Which ironically means Virgin are less likely to get the money...
Well I'm 6ft (though fairly slight build) and had a good amount of legroom, even when the person in front fully reclined. I wasn't a fan of the headrest (think LNER First but a bit less invasive) as I fell asleep on it funny and woke up with a sore neck.
In fact, it's probably the best sleep I've had on a long(ish) haul flight, neck ache for a moment aside. I think I had about four hours or so out of the seven hours flying. A can of their white wine with dinner (a naff pasta but US catering was never going to be great) and I was sleeping like a baby until just before breakfast (a muffin, granola bar and yoghurt with tea/coffee).
I will ultimately be quite biased though - as I also had an entire row to myself
It did seem to be more lightly loaded than Economy so a few people had spare seats.
For a hundred quid or so - worth it I'd say. As others suggest, you'll be given the chance to upgrade as you check-in (or even later than that).