My DH and I have a deal where he can do stuff without me IF he makes sure I have the phone number of someone who will come help me if I need help. It doesn't have to be someone I know well, just someone he knows won't flake out if I needed a ride to the hospital. I think it's a fair deal.
And don't forget that in a real emergency an ambulance will give you a ride to the hospital too!
If you get *super* stressed about it, you could try one of those medical alert systems. You know the necklaces where you press a button if you need help and they send help? (i assume you have those in the UK.. they are popular here with the elderly and people with heart problems or diabetes)