E Bikes (bicycle) advice

I am looking to buy a bike to improve my fitness and mood. At my weight and age hills are a no go. Thinking of getting an e bike for that bit of help when I need it.
There are so many options that I am getting bogged down with research. I will ride on lanes, tow paths and in Sutton Park and think I need a torque sensor to get proper exercise. There are so many mail order companies but not sure of the quality, I like the thought of Decathlon with the guarantee and physical shops to visit and some cost as much as a car.
Any views/advice/experience?