Hi Anja! You are doing the right thing. I started just like you with 8 30/500 over a decade ago. I didn’t start taking 8 a day but bit by bit every single ache or twinge became worthy of codeine. Before lunch by it was 9 a day, then 10, then 12. There really is no limit once tolerance starts to build. Your whole life then becomes about the pills. I agree with Magie that maybe a taper if you are too weak for the trip. Maybe take half what you were and taper from there just to get through.
If you feel strong enough to push on some diaohrrea tablets will help all your withdrawal symptoms. I took the maximum dose of 8 per day and then tapered down one tablet a day during the first well, 8 days of withdrawal ☺️.