yeah its not just the no shows but also the bad waiting times as you pointed out.
If they offered you a new appointment say 24 hours after the no show and also properly fully refunded your install fee (which in my opinion would be reasonable) I bet you would have gave them another chance.
In my case I had a circa 2 month wait for install following my order which made me escalate it to the BT executive office.
BT Infinity 2 Since Dec 2012 - Estimate 65.9/20 - Attainable peak 110/36 - Current Sync 71/20