I have sold parts of my round off in the past. I have always gone round with the guy and introduced him to the customers. This is only common courtesy.
I would have insisted on it, even more so with the round not being serviced for 4 months.
All you can do at this late stage is to approach the customers, and explain the situation.
I would only pay him for the first wipe, on the jobs that actually materialised.
He could whistle Dixie for the rest. Dai