I have trained in quite a bit of self defence with various different martial arts.
What training and instruction have you had on the laws governing use of force in defense of self or others?
The hoe could be lethal in a very unlucky scenario, as you say, if it struck an exposed neck, or major artery.
Is it reasonably capable of causing “grievous bodily harm”? Being rendered unconscious or otherwise unable to defend oneself, or losing an eye or other significant organ would qualify as “grievous” in these circumstances.
Would a person reasonably fear either “death” or “grievous bodily harm” from an individual wielding a hoe as a weapon?