If you have a hypo while driving, then no consideration is given to how long ago your previous hypo was!
It doesn't matter if you caused an accident, whether injuries to you or a 3rd party, whether any vehicle or property again yours or a 3rd party has or hasn't been damaged... You just need one of the emergency services to attend, normally it's either the ambulance service or police... But if the fire brigade are called then like the paramedic they will inform/call out the police due to dealing with a diabetic who's had/having a hypo... And the police will automatically revoke your driving licence and tell you to surrender your driving licence to the DVLA until you've proven your fitness to drive!
You will have to go through an appeal procedure, on your side is that you haven't needed 3rd party intervention before, so you'll just dealing with one hypo as such, but because it happened while you were behind the wheel, you will have to prove that not only is your control within the requirements to hold a driving licence, but you also manage your diabetes with due care and attention for driving...
Which is basically, that you have sufficiently before your journey even started, that you tested before starting your journey and at the point the incident occurred you hadn't been driving for a period of time that might put your control in question, such as that since your last meal/injection it's now 3 or so hours so it's likely that your blood glucose is dropping etc... This information will be based on your blood glucose meter