Payroll Bureau software for GPs

I understand the only main player on the market providing payroll software to GP Practices for payroll preparation is IRIS.

We offer a payroll bureau service along with annual accounts prep, tax returns etc. and do not fancy paying £400+ for an IRIS package we can only use one client on.  Finances aside, it isn't really feasible to install IRIS multiple times for each GP client we prepare payroll for.

Are there any alternative packages on the market?  Do Sage have a third-party module to deal with NHS Scotland superannuation deductions etc?

Thanks,

Andrew Morrison