// Osborne was arrested on suspicion of commission, preparation or instigation of terrorism including murder and attempted murder. //
I expect the charges will be revised.
The man who died was possibly dead already, we will have to wait to see the medical evidence.
I do not know the legal definition of terrorism, it is almost certainly different from the dictionary definition, but to my eyes he is a (attempted) murderer, and not someone with an ideological agenda. I doubt he will face terrorism charges.
Reports say he being treated for a known medical condition, and he was on medication. And his mental state is repirted to have worsen lately according to people who knew him. He had been binge drinking the day before, and acted drunk on his arrest. So the medical examination on his health will also be a determining factor on what he is charged with.
My guess is attempted murder, and a defence of diminished responsibilty. Then it is up to the jury if they believe that.