Bad service from Halfway Toyota Ottery

We booked our car in for a service months in advance due to timing. We got there on time and took out all our belongings and bags and said to the person receiving us, that we are going to sit and wait for the car. So they took the car and we kept ourselves busy for 2 hours and when I went to find out if the car is ready. The only person that was there came back to us and said she has bad news. The car was parked outside the whole 2 hours. They haven't touched the car and everybody has left to go to the mosque. It's going to take another 3 hours +. Nobody informed us that they will not be able to service the car and we sat there for 2 hours for nothing. We had to leave with our car as we brought it without getting a service. All the manager said was that we must make another booking and he will make sure they take the car the instant it gets there. For the petrol we drove out to get there and our whole day wasted where we could have done something else. Not acceptable