I switched in country from a non-partner visa to FLR(M).
First and foremost - stop worrying. You'll find the people on the day very friendly and helpful.
Only take in the required information, just keep the rest in your car (or bag if taking transport). They truly only want the required info and not a load of extra things.
My tips:
1. Do not use clips or post it notes as they may want them all removed anyways.
2. Do not give a photo or correspondence outside of proof of living together as they are not necessary. Just have them in case they ask (they'll never want a photo as a photo proves you've met and as you'll both be right there - they know you've met.
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)
3. At the door, they'll want to see your appointment confirmation - have that out.
4. The first stop after security, they'll want to see your application (just that) and possibly your payment receipt.
5. The next stop, they will want your photos, passports, and payment confirmation. They may want the application as well.
6. Then you'll have your photo and biometrics. They will then take the entire package from you.
7. Bring a book or ipad as you may have a long wait
8. They'll hand you your approval letter and send you on your merry way
Hope that helps a bit. Please do relax. You are ready!