there are a few things to keep in mind when choosing a kit:
1. avoid Chinese cells in battery. Battery cells are graded. Those failing A grade and B grade are sold off cheaply without branding and found their way into cheapest batteries. Also, if you buy batteries from a reputable UK source, they have insurance which covers fire risk.
2. Avoid parts with long cables. Generic parts have cables that are longer than necessary, when your kit is finished, you will have to get rid of the excess cables. The only way is to cut out the excess cables and resolder. Nobody wants to waste time and effort doing that.
3. Avoid non waterproof connectors.
4. Avoid motors without screw lid. One day you may need to open your motor, so avoid motors whose lid requires a special tool (usually called a spider) to open.
5. Avoid so called 1:1 controllers. They have low quality processor and firmware. Best choice are FOC contrllers that have STM32 chip.
Best brands for batteries are Samsung, Panasonic, LG, Sony
The common choice for cable system on kits is the Julet cableset.
The common choice for hub motor cable is 9-pin short cable (10").