I'd imagine they'd be High Anglican, if anything, so it probably wouldn't be seen as common. Religion is very much about respectability.

I can imagine them having something that uses the forms of religion but maybe has a different substance.

Even if Harry and the others were going to chapel every Sunday, they wouldn't talk about it in canon. Talking about religion here is akin to wandering around in public in your underwear - it's very rarely done and it's always greated with immense embarrassment.

Gah. It's only lunch - they could get away with skipping it and then I don't have to worry until I write an evening meal.