So the Agent from Harwoods was quite happy for you to continue driving it?
I think if it was me I'd be requesting a flatbed recovery truck as a repeat of the instance described where the steering wheel couldn't be turned is a lot more than just not acceptable. It's a judgement call based on the circumstances as you see them, but you have to ask yourself if there was an accident and third parties were injured, how would you feel?
Without knowing and understanding the operating philosophy, it's impossible to rule out it being mechanical, electrical, software, any combination of all three, or indeed a completely unrelated matter such as an extraneous item flapping and jamming the steering.
You could jack the front end off the ground, start the engine, and turn the steering from lock to lock to feel if the resistance changes; then have someone else do that whilst you look under the bonnet and observe the steering column - are both UJs moving freely, are the clamping bolts tight, basically follow the system through looking for something out of place.