Company policy at West Midlands Trains is to tell customers they're not permitted to depart early if their service is cancelled, but their ticket wouldn't be valid usually on the previous service
in the case of flexible tickets. I don't think this carries over to Advance tickets, where they adopt the more common position of the service before or the service after being advised. My view during the event when it happened to me was that they were obliged to carry me as close to the original arrival time as possible on one of their alternative services, but they refused to accept this. Whether they do this because they enjoy inconveniencing people at no benefit to themselves, or for some other inexplicable reasons, I don't know, as they wouldn't offer me any further detail as to why.
Unfortunately, if you'd like to travel on the preceeding service, it's advisable to ask therefore. My view is that this isn't
necessary, but I would probably do it. I wouldn't bother asking if I'm travelling on the following service though. In the case of Northern I understand that their policy is to allow the service before as well as after but they don't necccesarily go on record about it, unlike say LNER who are very open that this is their policy. It's worth asking Northern to confirm on the record, and seeing what they say.
A lot of the services from my local station are hourly, is turning up over an hour before the scheduled departure a likely thing for a passenger to do?
Yes, if you know that your intended service is cancelled, obviously? Otherwise this question wouldn't arise. Surely you can see that plenty of people will be fine with getting to the station an hour early, in order to avoid arriving at their destination an hour late?