Satellite C850-F0055 laptop

I am trying to figure out how to access the boot menu at power on.
I have tried f2 & f12, f2+fn & f12+fn, tried holding the keys, tapping the keys
holding for 1 second etc, I have tried all the f keys as well, tried esc, backspace
ctr+ del nothing works.
what happens when I boot up, within 1 second 'Toshiba Innovation' screen appears
and then proceeds to load Windows 8.1.
I can access BIOS/UEFI via charms-pc settings and navigate to UEFI and get in that
way but that won't help if I need safe mode.
My settings are:- ODD/USB/HDD, boot speed set to 'normal', Secure boot disabled
I have a dual boot system with Windows/Linux.
If I put a boot disk in and power up, the boot option is totally ignored but with the disk still in
and Windows loaded and I access UEFI via the above route, enter UEFI and exit again
immediately the disk bursts into life and loads the disk as is supposed to happen at start.

I have not sure where to go now so any help will be appreciated

Cheers Rozzer