HELP! I have brain freeze. Applied for a job, and had an email from director

[QuintessentialShadow]

It basically acknowledges my application, and explains they have had lots of applications so it will take them a little while to get back to me as they are reading through it all.

No doubt they have sent the same email to all applicants, BUT.

I think how I respond to this will count towards how they judge me.

It is a managerial post, with much of responsibility and autonomy. I will report only to the regional director (who emailed me).

I was thinking of keeping it brief. Just saying something like "thanks for keeping me informed, I look forward to hearing from you in due course, Best Regards."

???

That sounds fine - though TBH I dpn't think you actually have to reply at all. But it's a polite thing to do. Certainly keep it short and to the point - your wording sounds fine to me.