You're welcome
I would heartily recommend a service element being included in any bonus structure as I've seen too many people do stupid things to manipulate sales figures which will damage your brand.
The two elements to focus on are customer complaints and customer feedback.
I would advise having a process where customers can escalate any complaints to you if they remain unsatisfied with the response from the shop manager (address to write to, email address on till receipt/website etc). However, all complaints should be referred to the shop manager in the first place to respond to. If he's never seen the complaint then he can't be responsible for resolving it.
You should never penalise someone for receiving the odd complaint (trends and excessive complaints should be investigated and evaluated separately) as a well handled and resolved complaint is the mark of good management - because things do go wrong occasionally.
People are more likely to complain than praise so mystery shopping can be useful. Just agree what will be measured and how it will be scored in advance. You can give a score to each section and weight it to show importance. Some sections you may not give a score to (eg rate your experience out of 10 and comments as they are quite subjective)
ie Mystery Shop - Presentation of Store
Windows were clean with neat display of current promotion Y/N
Shop floor was clean and tidy Y/N
Till Point was clear of clutter with mandatory notice clearly displayed Y/N
Till point was manned Y/N
All visible members of staff were wearing name badges Y/N
All staff were smartly dressed in company uniform Y/N
Mystery Shope - Customer Experience
As a customer I was acknowledged by staff when I entered the store Y/N
A member of staff approached me to offer assistance Y/N
When approached the member of staff's manner was polite and friendly Y/N
The member of staff dealt with my query quickly and professionally Y/N/NA or...
The member of staff referred me to a colleague who dealt with my query quickly and professionally Y/N/NA
I would rate the service I received out of 10 as....
I would recommend this store to a friend Y/N
Other comments....
Good luck with the new store