FS -
I'm another who learnt at Bristol (PAPI's nearly always on unless you ask) and at the time I really couldn't tell whether I was relying on the PAPI's or not, although with hindsight I think I was drawn to the slightly low approach that they tempt you into. I certainly shared the concerns you mentioned in your original post.
For what it's worth, as soon as land aways started, the absence of PAPIs just wasn't a problem. So in my opinion, yes it's a legitimate concern, but no it probably won't give you a problem when they aren't there.