Hi and welcome to V-Flyer.
As I am sure you are aware delays are quite a common practice on all airlines, and with Virgin the LGW fleet is run quite tight and heavily that sometimes a small delay can take quite a few days to be made up because they don't have a/c just sat around that can step in to help sort any backlog.
Also, quite often a departure/take off delay is quite easily made up in flight time, so a 1 hour delay actually leaving, will still result in an on time or ahead of schedule arrival.
With regards to some reported issues on the LGW flight, we have had
this thread running recently, so you might find some of that useful.
I wouldn't say you have to take food/drinks on board, but I guess it will depend if you are happy with the usual economy offerings on a long haul flight. I suppose it never harms to have a few snacks just in case.
The IFE isn't the best on the current LGW a/c, there is no doubt about that, and usually it works okay and you have a fairly decent choice of films/tv shows. There are some occasions when there are some issues with the IFE, but obviously that cannot be predicted and to be fair it does happen on the LHR fleet with the better IFE.
Hope you have a great flight.
Neil