Got the answers to some questions from the guys at I-Lap. Firstly, their swift replies to my emails have been great, I hope their post sales customer service is as great as their pre-sales
In terms of damage to the sensors, they say that the sensors can be 2 foot above the track and some clubs actually place the sensors inside a clear tube when attached to the bridge over a track, thus preventing any damage to the sensors if a car was to hit the bridge.
Just waiting to get some feedback from some clubs who run it, but it's looking like the way forward for us...