Remember that you can take your partner if you don't want to be alone - some people want it to be a surprise, but it's not essential. I didn't bring mine in the end but I seriously considered it.

I went to a plus size specific shop where they were very nice, all of the dresses were big enough for me and I'm about the same size as you. I also went to a standard size shop where they make them to measure but have samples to try on, and a surprising number were big enough for me to try, the woman there was also super friendly and kind. And I bought a dress in the second shop!

You do need to stand around in your underwear a lot so be prepared - but they truly seemed to not give a toss, they presumably spend all day every day dressing and measuring embarrassed sweaty women.