What to wear to super posh barn wedding this summer

[pharmachameleon]

Going to a wedding in Sussex in July and I'm stressing about an outfit already. The bride to be and groom are so lovely and I know the wedding will be amazingly stylish and I would love to fit in. It's in a big barn with I presume a marquee. I think I'm okay with an outfit (Rixo dress) but not sure about accessories. Are fascinators really old fashioned now? If so what do you wear on your head?
Thanks

Rixo dress sounds good and would forgo headwear entirely! Get a great bag (or rent an expensive one?) and focus on gorgeous yet practical shoes if it’s outside/on rough ground.

Thanks @MrsJaneyLloydFoxe. No headware at all? I was thinking about some sort of sparkly comb or feather or something lol to elevate my outfit a little. I get fascinators are out though.