They aren't an established make, just bought in models using generally available motors and batteries. They are probably ok, but if you are spending that sort of money I'd recommend you buy from the well known and established brands which you know will still be around for years to come with support, spares and replacement batteries that fit. This isn't usually true of unbranded buy-in bikes.
For example, the eZee range from
Onbike are mostly at or around £1450 and eZee are one of the oldest established e-bike companies at 9 years now. Not only that, the replacement batteries fit every model they've ever made*, which is unique in this industry.
There are a number of other established brand names making good e-bikes in that same price area as you'll see in this forum
* The only exception, the Rider model, used widely available SLA batteries which are easily and cheaply user replaceable.
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