Mostly help up the hills, at the moment I have to get off the bike and push up the hill.That looks good. ridgeback is fine. Almost all brands use the same components; obviously lower end for cheaper models and higher end for expensive models, and pretty similar frames. There are lots of advantages to hub gears, but the gear range may be a little less than for a derailleur bike.
The 125km will be a very optimistic range; lowest assist, flat good roads. It may well not do 50 miles of real riding (***). The specs don't mention battery capacity which is odd. (probably 418wh?)
If anything does go wrong after guarantee any repairs or new batteries will be expensive.
(***) You didn't mention what sort of riding you wanted to do, how hilly, and whether you wanted lots of electric assist or just a boost to help you up hills. If you look at https://www.bosch-ebike.com/en/service/range-assistant/ you will see how much range depends on many factors; the broad comparisons will be the same for Bosch or bikes with other motors. Choose the Bosch 400 battery for a pretty close idea of what you will get.
p.s. Cheaper from https://winstanleysbikes.co.uk/ridgeback-electron-di2-2019-electric-bike
£1560, but only extra large?
Mostly road but the occasional gravel path