Thanks for the replies.
I'm not planning on wearing a hat...am not close to the bride & groom (groom is DH's friend, I've never met the bride) so hat would probably be a bit OTT.
Re the black & white thing - I did wonder. I know that white is an obvious no-no, & I always thought that black was too (however having read threads on here plenty seem to think it's fine) but I thought that black & white together would be okay...