My (sadly now deceased) T1 mother suggested that if you feel low on a motorway you should pull over on to the hard shoulder, chomp your carb, wait out the hypo, and tell any police that query this that you suspected the accelerator had stuck briefly.... (This advice was a decade or so ago, mind, and I can't now remember whether it was accelerator or brakes, but the point was that a car defect was making you pause for a while.) Luckily I've never had to try this out but my one experience of driving hypo (about twenty years ago) was extremely scary and I was very lucky that I didn't have an accident. I am now paranoid about vehicles and blood testing and haven't had any issues since.
From what I know regarding emergency stopping a motorway (Hard shoulder.) for whatever reason..
It is advised to put on hazard warning lights, turn the steering away from the carriageway. (This is to enable the vehicle to leave the road in the event if it should get "rear ended" out of the way of other fast moving traffic.)
wear high viz, (passengers too.) & more inportantly don't stay in or with the vehicle. (In the possible event of the aformentioned "rear ending" by another vehicle at speed?)
You probably more than likely going to be aproached by "highway agency" patrol to offer appropriate assistance. In the event of a breakdown, they will check you have cover & recomend the service does it's job? Then check back later to assure all is well..
I had a blowout heading south on the M5 about 13 years ago.. They wouldn't even let me undertake changing the wheel..
They were happy I took most of the other appropriate PP action at the time.