Outsourced payroll

A client has asked me to do their payroll.  They currently only have 4 employees, but will probably grow.

I only do a few directors £624 per month payrolls.  Although payroll is not too difficult with the right software, I really can't be bothered to have to be doing this every month, especially when RTI comes along.  I want to just e-mail the client with a few payroll bureaus and let them sort it out.

Can anyone in the community recommend some good bureaus?  I know I could just use Google, but have no idea which are good, which are bad or whether (as I suspect) they are all much of a muchness.

P.S. No blatant plugs from outsourcing companies please, as I am seeking the views of other accountants!