.when I take fiat out of coinbase it takes about 10 minutes to appear in my rbs account .
Are you withdrawing large amounts or small amounts? LFC_Bitcoin is probably talking about withdrawing hundreds of thousands of dollars?
Always under £1000
Then it doesn't count. We're talking about 5+ digit numbers here...
in the 2017/8 bull run it took ~24 hrs for 5 digit transfers to go from coinbase to my bank account. i did this every day for a period of days, and it was always there the next day.