@CXRAndy I have only used hub motors in the past but you are suggesting a crank one, can you explain why please? Are they more powerful, better suited to gearing?
They can be less powerful but with the advantages of gearing will get you up any hill.
I made a TSDZ2 crank motor for my wife. Its limited to 300 Watts max. She can get up hills easily-all she does is drop onto the easiest gear and still has 300W available ontop of her 120W, so climbing @420W-thats is alot of climbing power.
The more powerful Bafang BBSHD will add another level of power compared to the TSDZ2.
Id suggest you look to try a crank based ebike. You can hire E-MTB for a day at common cycle spots.
Regarding the bike, I looked at Genesis bike, the criteria I mentioned, Genesis do this model
https://www.genesisbikes.co.uk/bike/Smithfield-2020
Also the Brixton-derailleur version
A bargain currently
https://www.genesisbikes.co.uk/bike/brixton
Flat handlebars, big tyres, rack, mudguards and disc brakes
Now this is my Mrs Genesis Columbia bike(with TSDZ2)
-almost identical but womans shopper frame. I bought hers(new) for less than half price of retail, by getting the last year's model. Good deals are out there