You’ve got VAT and duty on top of that price and no warranty. I remember when fake carbon rims and frames were all the rage on that platform and people where needing face surgery after their headstock snapped.
a few Chinese brands have emerged as being ok, but then the copies get copied.
that bike looks like junk anyway.
To make a 1kw pack out of quality 18650 cells will cost £300 min wholesale. You’ve also got roughly 11 series by 8 parallel to charge and manage so it will need quality thermistors and balancing circuits which it won’t have. So the chances are it will not be holding a charge well after 6 months and may end up with a cell designed to charge at 4.2v getting more than double. Too much power to take a risk with
Costco have a few bargain ebikes.