Thank you all!
It seems that I could go with 195/50 tyres. Your car Rhysfjf is a bit lowered while mine has the original suspension. I don't know if it matters? Probably not...
It's a pity that I can't change to summer wheels yet. I got an offer for a cheap set of new Advanti Chrome wheels but it's a risk buying those wheels before I'm absolutely sure that they don't rub. Those wheels were bought for a Toyota Yaris but that car crashed in an collision.
That will definitely make a difference. I'm lowered by 40mm and when I go over quite bad humps in the road at speed the wheels do catch the plastic wheel arch on the outside very briefly, they've actually caused the plastic arch to split but it's nothing for me to be concerned about - I can get pictures if you really want. But as you're on stock suspension I highly doubt you'll get that!
I could probably actually stop it doing it by removing the lining or cutting it back slightly or something, but it's so minor I've just left it. I don't get any rubbing on full lock, so they're spot on. When I get round to changing the tyres I will likely go to a 195 to see if it helps.
Hope that helps!