This is the controller I bought, KT is the brand
Zen Cart! T09S 36V/48V500W 22A KT Sine Wave Controller For ebike [T09S KT 9Mosfers Controller] - ★★★★★ T09S 36V/48V450W-500W Torque Simulation Sine Wave Controller For ebike 1--Rate Voltage: 36V/48V Compatible 2--Maximum Current:22±1A 3--Low Voltage Protection:DC30±0.5V 4--Speed Set: 1-4.2V...
topbikekit.com
The same site has akm128 hub motors (2.8kg) although they are rated 800w so not UK legal. There are 250w rated hub motors on that site
Zen Cart! AKM-128H 36V/48V 800W Rear Driving Hub Motor with 20/26/28inch wheel rim [AKM-128H 36V800W] - ★★★★★ AKM-128H 36V/48V 800W Rear Driving Hub Motor with 26inch or 28inch wheel rim Specification: 1. Voltage: 36V/48V. 2. Brake type: V-brake, rim brake and disc brake are compatible 3...
topbikekit.com
I know some people learn by experience but as
@saneagle said, if you fit this kit to a bike with rim brakes you'll be constantly adjusting and maintaining the brakes because of the extra weight , power and speed (and it's so much fun you'll be using it all the time) and it will wear the wheel rims. You can get perfectly good old bikes off Facebook with manual disc brakes for £50 and then upgrade them to hydraulic brakes (I got a pair of Shimano mt200s for £35 from Ali express) - takes 20 mins max to fit them. They will last thousands of miles of maintenance free and worry free braking