We have just gone through it, so it is very early days for us. Our infants and juniors are physically very close to each other, so work is underway to link the 2 schools with a central entrance and office, with corridors into each school. A lot of money to spend considering we are a 30 second walk along the path to each other. But psychologically it will be worth it if it makes it seem like one school for the parents (and us).
Our County has a policy of amalgamation of separate schools if one of the headteachers retires and this is what prompted ours. The remaining head took over the headship of the 2 schools in an acting capacity. I can't see them having to reapply for their own job as they are thought of highly within the County ed dept.
There has been no mention of re-structuring or reapplying for our own jobs. I have heard that this is what happens if a school becomes an academy, though.