It is up to each employer to choose a pension provider. We can't help you choose but you can get help from The Pensions Regulator or an independent financial adviser.
The Pensions Regulator's website has a list of providers. It says you should pick a scheme that either has master trust assurance or is regulated by the Financial Conduct Authority.
You must tell your pension company about your staff and their pension contributions. Many pension providers let you do this online but our system gives you easier ways to transfer your data to the following: