Not sure if this applies to anyone else but thought I'd post it here in case it does.
I just phoned National Rail Enquiries and they said that if the strike does go ahead then there probably won't be any Virgin services directly to Oxford from the northeast, Yorkshire or Scotland. They said there might be some GNER services to London running but they aren't sure if cross-country tickets will be usable on those trains. They also don't know what will happen to trains that are in the middle of their journeys when the strike starts at 12 noon on Friday.
So basically they don't know much, but if people find stuff out they could use this thread for updates.