I fully suspect that had Minardi survived into Formula One's current age, they would be in the top three of almost everyone on this site. So I don't think there's any overt nationalism involved. Indeed, if you think about it, there's been very few occasions where the Scuderia have been a direct opponent to a British driver's title tilt. Hunt/Lauda, yes. Hamilton/Massa, yes (although I think Alonso was the media's 'enemy' at the time).
I do think that due to a surfeit of teams based in Britain who have thus more frequently run British (or English-speaking) drivers, there's a unique lack of attraction of Ferrari in Britain as, depending on era, Britons built a bigger connection to Lotus, Williams, McLaren, Brabham etc.
So, in short, I think being British increases the likelihood of an F1 fan supporting a team that has likely crossed swords with Maranello, but that is not necessarily due to Union-Jack-hoisting, God-Save-the-Queen-singing patriotism.