Fat bikes (generally, bikes with 4" + tyres) are hilarious to ride but they're not exactly necessary for day to day off road if the sort you describe. They're great in sand and snow but you need lots of sand or lots of snow to make them worthwhile.
A regular MTB would do everything that you describe and be easier to live with on a day to day basis.
Equally a "gravel bike" may well meet at least 95% of your requirements too. Note that gravel bike is a fairly broad term that can be used to cover hybrids, and "slightly beefed up road bikes" at one end of the spectrum through to "nearly a mountain bike " at the other.
The bikes you linked to look like sort of poor quality direct Chinese imports and I'm not sure they're all UK legal either.
First thing - set your budget.
Secondly, decide on e-bike or regular. There's nothing wrong with e-bikes at all, they're brilliant enablers and especially for people coming back from health issues who may lack strength to pedal regular bikes far. Ideally, if you've not ridden one before, try and get a test ride, even if it's only one of those Lime hire bikes you see in some cities.
Having decided on the "e-bike or not?" part of it, look for reputable dealers and shops, ideally UK based. There are a couple of e-bike magazines and websites/review sites now so try something like https://www.cyclingelectric.com/ for a run down of reputable brands. Be aware that for anything of decent quality, you'll be pushing the limits of your £1500 budget.
As already mentioned, Decathlon is worth a look - some of their mid range stuff is really very good indeed, excellent value for money and often getting good reviews. That £1700 Rockrider you linked to looks fine.