Last time I was at a rather grand summer wedding, many guests were wearing floaty dresses very like this one. Many were silk from LK Bennett or more expensive brands, but, to be honest, to the naked eye they don’t look a lot different. It all comes down to fit and cut - and the OP says it fits like a glove.
If in doubt , add expensive looking shoes and a fabulous hat.
I feel that very tailored structured traditional MOB and MOG dresses look a little outdated now.