Human Resource Consultant

I am a UK startup who wants to employ a specific former colleague, potentially on a zero hours contact ie can vary hours up and down. I am looking for someone who can help me onboard them - 1) compliance with UK law 2) employment contract, templates 3) pension, holiday, NIC etc. My accountant will administrate payroll however I need the above services from one up to date with UK law. I expect to employ additional staff in the future and seeking ad hoc assistance in the future.