I think your interpretation of how a PHEV works is a little bit off.
“but when the electricity has run out you are left with that puny 1.4l engine”
I drive the outlander PHEV and have never experienced the electricity “running out” and being left with a slower car. It is just not the way they work. Even when your prestored electric miles are used the car’s engine will power the battery and your still left with a hybrid drive that utilises both. Your MPG will be a lot less but you won’t suffer a loss of speed or pull away as a result.
Personally having moved to a PHEV I would never want to go back to a Petrol or Diesel engine. Such a great driving experience even in the brick like Outlander.
I agree with the comments about infrastructure although it has massively improved and will continue to do so. If you regularly make longer trips a PHEV is the best option. If you don’t then go the full electric.