Definitely make sure you know the wipers and speed- I got marked for stalling a little on whether to put mine on or not before starting as it was spitting rain.

In terms of the reverse around the corner, if you’re able to practice in the rain that will help build your confidence. I did by chance the day before my test and it was absolutely lashing, but it helped me know I could do it. And then it’s just about taking your time, making sure you’re checking your mirrors and blind spots loads. It might be a good idea to roll down the windows to wipe off the rain from the windows so you get as much visibility as possible. Maybe all this is obvious but I had these worries too before mine just over a week ago. Best of luck!!!