As to needing (or wanting) the parking aid, the car is my 17 year old daughter's and I am betting £80 on the kit against £800 for a new bumper......its not the length of the car I'm bothered about but the low walls, bikes and bollards she won't spot!
I think its a good idea, i find the 107 hard to park, you all say its easy because its vertical and small, but between the back seats and bottom of the car, its one huge blind spot, i reversed into a metal stand (loose) and i now have a nice scratch on my rear bumper

and thats in a source of 7 weeks driving the 107
Jake