"Mmm, I made a slight error in the read back of the information".
I think you will find that in the legal world that is not enough to get you off, being as you profess to being a barrister.
So, to your two questions.
Q1: "Do the CAA regulate this service?"
A: Don't know, but if you wish I will bring your "slight error" to their attention.
And what was your second question?
Q2: Oh, that's right "Should I bother to complain to the airfield and or the CAA?"
Hey, you are supposed to be the barrister here and you are asking us?
A: Only you can decide if you can be "bothered to complain". But perhaps a phone call to the "radio operator" and the "CAA" may be the first option that I would explore. But if you are after compensation for hurt feelings, well, my money is on you don't win. But, hey, give it a go if you think that you've got a genuine chance of winning.
Welcome to the real world. Reread line one and maybe do a little more study and gain a little bit more experience before judging others.
