Hello,
I'm so glad to share that I got the approval of my spouse visa renewal yesterday! It was such a long journey to get all the documents together but glad it all went well.
I thought I would share my experience in case it's helpful to others - I went to the Croydon Premium Service Centre. We arrived about 25 min early but were told to come back 15 min early - I saw others being turned away for being there too early - so they seem pretty strict that you can't enter earlier than 15 min before your appointment time.
We could use our laptop / charge it / use the phone, etc. in the cafeteria area. This is where we were told to wait after getting the ticket number through the "Reception" on the 3rd floor to then be called in to submit the actual application. It was about an hour between getting the ticket number and getting the call to submit the application.
After submitting the application, you get your fingerprinting done and the photo taken as well. Then we were told min 2 hours wait and could leave the building if we wanted to. So we went to get lunch nearby and came back to wait in the cafeteria area again. I got the approval in hand about 3 hours after getting the fingerprinting done - so all in all, it was about 5 hours by the time it was all said and done.
In terms of the documents, they asked me to take off the paper clips, binder clips but they said staples are ok. It wasn't a big deal, though. They just asked me to put the originals and copies in 2 separate clear binder folders they gave me. I had brought all my children and husband's passports - my kids are already British - so they're not dependents that needed to apply for visa but brought them just in case as the application isn't clear - but they said they don't need it - so they didn't take them. My husband has a dual-citizenship and they only wanted his UK passport and not the other one either (it sounded like they would have wanted this other passport if it contained a Home office stamp but otherwise, they didn't want it). I had also filled out the first few pages of the application on the payment information. They said actually no need to fill it out and for risk purpose, best not to. So if you're doing a premium service, they said don't fill it out.
Thanks everyone for all the help! I think I need to do this again about 2.5 years from now... see you then!