If you have outsourced your services how do you know they are delivering on the values you require or have requested?
It is important to ensure you have measures and monitors in place to regularly review what is happening across your estate to ensure you are getting the value you require.
Make sure these are independent from the outsource agent and like any monitoring system can be quantifiable and tracked over a period of time.
This will give you a picture of how the agents are performing and where your attention may need to be directed if one particular area is failing.
Should action be required you will have quantified evidence to support your findings. Although if it comes down to this it is likely that the relationship has already started to breakdown, have you got a back up plan?