Andy, as the radar was set up for the vehicle from the factory within the factory alignment settings, then the radar should be accurate within those tolerances.
Carrying out wheel alignment within the factory settings, (ideally as close to optimum as possible) there shouldn't be a problem. As long as the steering angle is checked or reset as required.

Devils advocate:
The get out clause "well you touched it last" is just that, an excuse not to do it.

Driving down the road hitting a pothole, dropping heavily off a kerb or other end user abuse, always has the potential to disturb the radar or wheel alignment. So if you think they're going to come after you, make sure your liability insurance is up to date.

Tony