Hi Liam,
Your potential A&P pathway is the same as the rest of us no matter what licence you hold.
1. Register on the IACRA website to get a registration number. You will also need a US contact point/address as you are a foreign agent. There are companies out there that provide this service.
2. Fill in and submit form 8610 with your qualifications and experience to an FAA Field Office where you will be assessed and advised of suitability to progress. You will have a interview with them as well which can be done over Zoom or in person by appointment. You will need a letter from your employer stating your suitability and requirement to hold an A&P such as working on N reg aircraft.
3. Get the Jeppesen A&P exam study guide books for general, airframe and powerplant, and the Prepware app. Learn the questions and answers. Once you start hitting 90% consistently in the practice exams, you are in a good position.
4. I do recommend booking in with a school mainly for learning the practical stuff for your appointment with an FAA examiner. The school will teach you to the exam. I'm B1.1 so had little/no experience of timing a magneto, wooden structures and piston engines for example so found this helpful. The FAA exam is a lot more GA level based knowledge. They will also take you through some of the FAA forms, checks and required wording. You take the online exams through the school at your own pace. I did all 3 exams in my first 5-6 days, and then prepped for the oral and practical with them.
5. Book in with an examiner. The oral and practical now has to be done over 2 days based on your exam results. Most of them will be flexible if you explain you are from overseas and on a schedule.
From what I hear the schools are pretty busy so you will need to book in advance. I think the cost for the 2 weeks was US$2.5k + exams + examiner. I went to AvTech in Riverside, LA and they got me through with no problems.