I’m responsible for appointing contractors for all types of work, including this.
I hire people I know or, if it’s a new area for me, based on recommendations from colleagues or my network. Only if I don’t know anyone and don’t get suitable recommendations do I look at the market and ask for quotes. People do business with people, not companies. I have used the same external IT team in my last 3 roles. I know that makes it difficult, but best bet is to build on existing relationships and forge new connections