I've never been on a mystery coach tour but I did once go on a mystery train tour. We did not know the destination until we had been travelling for an hour or so and then we were told where it was going to. We could either go to Ramsgate or Margate. We spent the day in Margate and then caught the train home at about 5pm.
when we landed at Antalya airport a few years ago, after 2 and a half hours on the coach we thought we were on a mystery tour, apparently that was the way they dropped people off, we were staying in alanya and last to be dropped off, it took nearly as long a the bloody flight!
staying at a Greek hotel once, we went on a mystery dinner trip and ended up at the taverna next door. In spite of tricking us out of our drachma the country's economy is still in trouble, so serves them right.
My mum on holiday in Bridlington took a mystery tour and went to Pontefract castle. She was not happy. On the guided tour they were told that Richard the third was killed there. Not so said Mum he died at the battle of Bosworth field. The last English king to die in battle. About two weeks later after her complaint she was offered the job of tour guide. I can still hear her laughing.
A friend of mine was on a weeks holiday on the east coast. She booked a mystery coach trip and ended up in Wicksteed Park in Kettering. She lives a two minute walk from the park......spent the day at home waiting for the trip back to the coast.