You should ensure that the person or company you employ is aware of the regulations and will carry out works, which comply with them. 

You can employ an Approved Plumber who will be familiar with the Regulations.

Contractors

You should obtain a set of the regulations, amendments and the guidance documents from HMSO or a Water Regulations Guide from WRAS and ensure that you carry out work according to the regulations.

You can apply to join WaterSafe or the Water Industry Approved Plumber Scheme (WIAPS) to become an Approved Contractor.