Hi
I have flown UC from both Gatwick and Heathrow and have to say it's brilliant BUT the Orlando route is definitely not the best but it's still good. I've now been to the Caribbean several times UC and the service and state of the planes is definitely better than the Orlando route, in my opinion. Virgin just don't seem to pay as much attention to the Orlando route as others.
Have to say that if you can afford it, go for it as you don't get jet lag in UC, well I never have and it's still a great experience. I love the luggage allowance as well, especially for the US - all those shops and bargains.
Have fun.
Tina