Which chain of restaurants is this?
As said above, you won’t get much loyalty from large commercial jobs, especially those that are part of multi site shops or restaurants. The new guys will have come in and said we will clean all of your stores, at £x price per store, and you’ll have just one invoice to pay. It’s a tempting proposition for the accounts department, save money AND save time paying the invoices. Unfortunately most of the time the level of service drops considerably.
If you want to chase commercial work, which I do, I find stand alone offices, (usually on business parks) are the absolute cream jobs.