I agree that £900 seems expensive. You may find you get better value booking your hotel and flights together on the BA website.
I haven't been in Virgin Economy for some time, so don't really feel I can compare the two products. One watch out would be aircraft choice with BA, if you are looking at Economy to Newark, then there is a good chance of being on a Dreamliner (Boeing 787) which is configured in a very tight 9 abreast setup in economy and certainly not recommended by many on here (Virgin also have this on their 787s). One other thought is that Virgin Airbus A330's and A340's have pairs of seats along the full length of the cabin which are nice for couples in economy.