If the size is OK, go for it, but you need the LED display to go with it, so £40
I just checked the BMSBattery website. For a few pounds more, you can get their S06S with S-LCD1, which would be a much better option. You'll also need their cheapest wheel speed sensor to go with it. It's the same sixe as the Ebay one. You still need to check if it's small enough.