That’s exactly the same treatment I received when I ordered my latest car. I turned up on time but was left waiting by the “specialist”. He eventually walked over about half an hour later and said “I’ll be about 20 minutes”. No apologies or explanations, so, like yourself, I got up and walked out.
After having the worst new car order ever, I too am beginning to get that “It’s only a Motability customer” feeling as well.