madmum , how deos he have an interview if the form hasn't gone off?
Don't worry... it may not always feel like it on this forum, but honestly there are lots of schools dragging their heels as much, or more than, your DSs! Lots of DCs on theis forum have got through the UCAS process really early, for a host of reasons.
I myself am trying to be philosophical, despite also gnashing my teeth at my DS's school and its 'ways'.