Three things you can do next. None of them need a diagnosis.
1/3 Talk to your GP
Book a double appointment so you're not rushing, and start with the words "I would like you to consider a referral for an ADHD assessment". Bring a short list of how it shows up in your day, and you can ask them to consider a referral under the NHS England Right to Choose framework.
2/3 Choose your route
NHS is free but the wait is commonly two years or more. In England, Right to Choose may offer a faster NHS-funded option if you are eligible and a suitable provider is available. Waiting times vary. Private assessment can be quicker, but costs, waiting times and follow-up arrangements vary. Check these before you decide. None of them are wrong, they're just different trades.
3/3 Build scaffolding now
You don't need a diagnosis to start helping yourself. Body doubling and the 1-3-5 brain dump are the two we'd hand you first, both free, both work tonight. Chapter 4 walks through all six of the tools our community keeps coming back to.
Important. A screener is a signal, not a diagnosis. Only a qualified clinician (psychiatrist or specialist psychiatric nurse) can diagnose ADHD in the UK. ADHD often co-occurs with anxiety, depression, autism and dyslexia, so a thorough assessment matters.