We went to London - Boston and then JFK - London in economy last year. It was with AA/BA not Virgin but I imagine the standard is pretty similar.
On the way out (mid morning flight) we got a hot lunch with an alcoholic drink if you wanted it, then free non alcoholic drinks throughout the flights and a hot drink and some biscuits about a hour before landing.
On the way back it was an over night flight so we got a hot meal again with a free alcoholic drink if you wanted and free non alcoholic drinks through out (although over night you needed to call the staff rather than the trolley going up and down). Then as we were flying over Ireland in the morning we got breakfast - so a hot drink, juice, yoghurt with granola, a bread roll and some fruit.
Entertainment was good, there was plenty of choice of films, music, TV shows etc.. I watched Barbie and the Holdovers and then Bridget Jones and a lot of Slow Horses episodes on the way back.
Take your own headphones - the free ones are terrible!
If you have only ever done short haul to Europe then the plane will be a lot bigger than you are used to, with a big middle section. Sadly the room in economy is similar (ie not a lot) so be prepared for that.
As people have said it is only maximum of hours so it won't feel that long really.