It appears that Virgin have put tickets for sale on their web site for their first domestic flights – LHR to Manchester from 31 March 2013.
The cheapest fare appears to be about £110 roundtrip. 2 flights per day in each direction.
The BBC are reporting that the flights to Scotland (Edinburgh and Aberdeen) are supposed to start on the same day but do not seem to be bookable at present. The also say that the service will be provided by Aer Lingus but in Virgin livery.