Good friend of mine who actually lives on 320 route would class that as a good trip as from what most drivers will say "An empty bus is a happy bus"
Seriously though you'll be surprised how many services around about this time seem to die a death passenger wise, there's even a few round Greater Manchester, take First Oldham Depot's 59 route for example quite a busy commercial service during the day but take 23:11 Middleton-Oldham Mumps journey for example, I've done this trip many times with various driver friends of mine from Oldham Depot and you can actually go all the way from Middleton-Oldham quite regularly without picking anyone up and as far as I know its commercial aswell and not tendered.
Sorry for going off-topic but just wanted to show that its not just 320s that have quiet runs other services by other operators do aswell
RE: Arriva St Helens