Susan - the layer that moves has been re-allocated.
I thought it was showing other faults but that turned out to be a remote instance of XP on public libraries. They don't refresh, the surfer has to, which is significant if I change anyhting. But I spotted another problem and sorted it.
The alt weeks question will be addressed in future but it depends on getting a datum for each event, which changes when there is a K in the month, a Bank Holiday or the event has to give way to a wedding or something.