I got Carrot with black box because it was by far the cheapest option for me. I drive a small 1.2L car so am not really that capable of speeding anyways. Overall, it's been good. The Facebook page response time is fast and they always give complete responses. I've had to message about once a week as the technology is still a bit rudimentary and sometimes gets the speed limits wrong, but they always fix it straight away. The only suggestion I'd have is to definitely pick sufficient mileage otherwise you have to pay for it, the black box measures your miles so you can't go even a bit over. I just got my reward card (which is just a MasterCard you can use anywhere) and am starting to spend the money I got back which is brilliant. Definitely would recommend this to build up NCB and also if you drive well you can get listed for significant renewal discounts.