Vehicles should be parked in such a way that the whole vehicle is within the designated area, so if the van is overhanging into your disabled space then this could be viewed as an infraction. However, the law around disabled bays can vary - if the space is marked by a white line then it is an advisory restriction, whereas if it is marked by a yellow line they are enforceable by law. We would suggest speaking to the business and pointing out the issues you have - it may be that they're simply not aware. Residential parking is usually controlled by your local authority, so you could also contact them.