A bit more on mid-drives...
'High drive train wear': for the use you describe, given basic maintenance of cleaning and oiling the chain, and replacing when it reaches the 'wear limit' with one of good quality, you can expect to need one or possibly two replacement chains per year, at a cost of £15 or so each. Cassettes will last considerably longer. UK legal pedelecs are not in the same ball park for this issue as monster motors putting several kW through the chain.
'Unreliable': buying new, you are covered for the warranty period, and worth checking how long that is. A quick Google suggests 3 years for Yamaha, only 2 for Bosch and Shimano. Out of warranty, yes, repairs are expensive because they tend to be replacement of entire motor / battery rather than mend. But how many fail? And of those, how many were thrashed to within an inch of their lives at every opportunity? If the failure rate was particularly high my feeling is we'd be hearing more about it. For a well looked after bike doing moderate mileage, and not subjected to pressure washing of the electrics!, chances are it'll go on for many years.
And the positives:
Really natural riding experience. It's you riding a bike with bionic legs, and you can turn up the bionic really quite high.
Helpful for fitness improvement and weight loss because you have to work to get the bike to go at all. Just not very hard, unless you want to. You can work as hard as you like, and then always have the comfort of knowing that just turning up the assistance gets you home with minimal effort when you've done enough for the day.
Great on hills, as long as the motor torque rating is high enough, and the gearing low enough. No limits really. For the gentle use you describe, the ActiveLine would do the job, but as
@Poolepete describes in his review, a higher torque unit is yet another whole new world! You might want to future proof with either the Yamaha or the Bosch PerformanceLine. Hills just melt away with a suitable bike, don't let them constrain your outlook.
The other parameter I would look carefully at is battery size. Low end bikes are still being sold with 400Wh and 500Wh batteries, whereas higher end have 625Wh or 750Wh. A spare battery is an option to add range, but it may be cheaper to choose a bike with the larger battery to start with.
Edit: just for clarity, I mean mid-drive with torque sensor, which all major brands have, but not all conversions.
