What are the sources of surrogates?

It is the responsibility of the genetic couple to find their own host. The infertility clinics in the UK are not allowed, by laws, to make host surrogacy arrangements.
The surrogate can be known or anonymous. Known surrogates can be relatives such as sisters or friends. Whereas anonymous surrogates can be arranged privately. In the UK through non-commercial voluntary agencies such as COTS and surrogacy UK.