[macmac]

Break an old thermometer into his cup of tea

tony

[Londoner]

It would make a lot of difference if the old WC does a handover and introduces you to the customers etc.
I have a slightly different situation where we have just leafletted a new area and picked up several new customers who tell the same story. Their old window cleaner finished due to health problems but the promised new WC has not showed up after several months. So now they are mine.