I wouldn't say i am a big formula 1 fan, but in the past i have seen the F2 races on in the background when watching Sky Sports F1 live.
Because i don't watch NowTV Sports on Demand where i can, where i try to avoid it because i hate 25fps playback for NowTV Sports on Demand.
So i can't say if i have seen F2 races in the past on NowTV SOD ( either full repeat or highlights) on the NowTV Sports on Demand service.
Please Note adding content to NowTV SOD can take between 24 to 48 hrs from what i have seen on their service in the past.
Hopefully a F1 Fan will confirm either way about the F2 Races.
If you get no response on here from NowTV F1 Fans about F2 on SOD, then maybe ask NowTV the question directly by sending them an email using the email address on this screen shot below.