Virgin does not have a first class service, only business. And they do not permit two carryons (although enforcement of this rule varies), unlike almost every other carrier.
United has three daily flights between ORD and LHR, all are new configuration 767's, which have fully flat bed seats in business as well as decent on-demand in-flight entertainment. Service is, well, United style, which means variable with a tendency to be average or below.
You may find the most cost effective business ticket is a one stop service: Air Canada via Toronto.
If you are not able to buy sufficiently far in advance to get discounted business class directly from the airline, consider going through a consolidator.