S6 Bricked (Can't get into recovery, not detected in Odin)

I have a Samsung Galaxy s6 (GM-920F I believe) and after a OTA update to the Marshmallow firmware, it fails to boot up on the Samsung logo (it displays it but doesn't make the sound) and I cannot use the volume keys to access recovery (or download mode). In addition it isn't detected by Odin on vairous PCs (and I've used lots of different micro USB ports). Any help would be appreciated. Thanks