[SimonPStevens]

The formal certificates will help in some situations, but don't assume you need them for everything right from the start. Speaking for myself, I would have happily hired a consultant with the experience of being blind themselves over anyone with a certificate.

Another thought is that for one of the projects I had the accessibility requirement came from the UK government. It was a project being used in a public service department and it was a requirement for them that every bit of software they purchased was accessible. If you're in the UK you may find the public sector is a good place the look.