This link may help
http://www.diabetes.co.uk/driving-for-work-and-blue-light-services.html
While there may be no reason why you can not be a HGV driver remember you are on a restricted license which can technically and legally be taken away from you at any point should you have any medical complications.
One of the annoyances we all have to deal with is constantly updating our driving license. On the plus side its nice to always have a shiny new one
When my wife and I moved we made sure we lived near a train station just incase I am unable to drive further down the line.
As a diabetic you are banned from driving Emergency Vehicles
If treated with tablets you may hold a licence to drive either a large good vehicle (LGV) or a passenger-carrying vehicle (PCV).
If treated with insulin you lose your entitlement to drive the C1/C1+E class (including categories C1, C1E, D1, D1E, C, CE, D or DE)
This includes vehicles between 3.5 and 7.5 tonnes with a trailer, up to a combined weight of 8.25 tonnes.
However, you may apply to be assessed individually for fitness to drive these must vehicles must meet a number of conditions which can be found in the above link
I hope this is helpful
kind regards
Matt