Undertaking the vehicle in front is inherently dangerous and hence is why it is an offence. It is DEFINITELY driving without due care and attention. If the vehicle in front stops suddenly FOR ANY REASON and you are having to change lane suddenly 'to avoid a collision' as you put it, then you were likely to have been driving too fast and too close so as to avoid a collision (ie tailgating). What if you were unable to change lane and collided with the rear of the vehicle in front? Would you have blamed the other driver? As a member of the Institute of Advanced Motorists (and an advanced Motorcyclist trained to Police Class One Standard), I often see drivers who are exceeding the limit, aggressively tailgating the vehicle in front to intimidate the vehicle in front to either speed up or move aside so the speeding tailgater can then accelerate towards the rear of the next vehicle and repeat the process. If this fails, the offender often undertakes the vehicle in frustration. This type of driving is, at best anti social and, at worst, dangerous and illegal. And, when drivers are caught, they ALWAYS have an 'excuse' and it's ALWAYS someone else's fault. Drivers are generally oblivious to the amount of road needed to safely come to a stop in an emergency. They rarely drive appropriately according to the conditions (how often do idiots in cars drive without their DIPPED BEAM headlights on in fog, rain, low light conditions? Especially in grey cars - the majority of cars being grey in colour - rendering them virtually invisible to other road users). You have commited (at least one) offence. You have put other (potentially vulnerable) road users at risk. You must face the consequences. You would do well to learn from the experience and strive to reflect on your driving manner for the future rather than worry about how you can get away with it and the financial implications. Why not look into improving your driving with a IAM 'Skills for Life' course, or via ROSPA, etc.? And before you start with the "I don't need to improve my driving - it's the others on the road who are at fault" diatribe, the fact that you are having to attend Court speaks for itself. You are likely to incur a fine and get points on your licence. And this WILL have implications when it comes to vehicle insurance. Good luck.