Yes, you can get a private ADHD assessment without a GP referral. When a referral is and is not needed in the UK, and how to self-refer and book online.
Can You Get an ADHD Assessment Without a GP Referral?
ADHD vs Anxiety: How to Tell the Difference
ADHD vs anxiety explained: how they differ, why they are so easily confused, how they overlap, and why a proper assessment matters to get the right support.