First of all: When you get the forms asking for consent. That means that a referral has already been requested (for which RM pay a fee), and they're just asking for your consent to actually turn up. So they'll probably hold a refusal against you, even though it's immoral to do so.
Secondly: It's possible for you to INSIST on seeing a fully qualified ATOS Doctor. I only found this out fairly recently, and my experience of ATOS has changed completely, since I started doing this. Obviously, they're still biased towards getting you back to work ASAP, or retiring you on health grounds. But because they're properly qualified, they aren't likley to send you back too early, causing a second sick absence. And far more importantly in my experience, they can sometimes suggest alternative treatments for you to suggest to your own Doctor.
Your DOM won't like you insisting on seeing a proper Doctor, because ATOS have very few of them left. So there's often a much longer wait to get a face to face appointment. And it also costs RM more money, because it costs more for ATOS to provide a Doctor's appointment. But that's their hard luck. Your health is more impoirtant than their budget. Never let them tell you any different!