Wow that is really cheap! £150 for this and that's the whole kit (I think) for £200.Maybe you should try to focus on a 500W 48V geared hub motor. That could be a good match. Bafang used to do one and I'm sure there are other options, these are super power hub motors right up close to middle spec mid-drive motors for hill climbing performance.
I don't know if it will help you but I wonder if this Bafang wheel currently on offer could be over-volted to 48V from its stock 36V? Perhaps someone else knows the model knows. It's the G020 model I believe.
Ebike Conversion Kit, KT Control System Kit, for 500W /750W Ebike Motor, KT 22A Controller and KT LCD3 USB Display Without Motor Wheel : Amazon.co.uk: Sports & Outdoors
Shop Ebike Conversion Kit, KT Control System Kit, for 500W /750W Ebike Motor, KT 22A Controller and KT LCD3 USB Display Without Motor Wheel. Free delivery and returns on all eligible orders.
www.amazon.co.uk
This is the other one I'm looking at. I believe it's from the same line.
BFSWX02 48V 500W - G020.500D/DC mode
https://www.amazon.co.uk/Conversion-Wheel-Electric-BAFANG-Display/dp/B09R7TDWHJ?th=1&psc=1
I guess the question is whether it's worth spending more for the native 48v hub kit?