Help greatly appreciated - S6 G920F Bootloop after odin flash

Hello folks. Today I did a cache, system, data wipe in TWRP on my G920F. After that I tried to restore a nandroid backup, but it failed and when I tried to restart it said there was no OS installed. So the phone wouldn't boot. I figured I did something wrong so I downloaded a 5.1.1 stock rom (UK) and flashed it with odin. But after the flash the phone would just bootloop. How can I revive the phone? Tried flashing the firmware again using another version of odin and also, I did a factory reset from the stock recovery, but no dice. Any ideas? Thanks in advance