Its only a very rough estimate. We went from Portsmouth to Cherbourg in August this year and I can't recall exactly but the fare was somewhere in that region. Two adults and two children plus Vauxhall Zafira. It might be more to Roscoff because that's a bit of a longer journey isn't it?
I would have thought so, just wondered how much it goes up by in peak season. I can get 20% off if I book the accommodation I'm currently looking at but wanted to work out roughly how much it will cost over all.