Many thanks for the helpful responses. Some interesting stories also to consider.
I actually did half of my PPL on a Warrior II, and never really had any concerns about the safety of the design. It was a pain to get in and out of, but that was it.
It was only after I recently received my PPL and considered the possibility of taking up friends and family that I began to worry much more about the safety of it.
With my current situation, I would probably need to decide between either the C172 or the PA28, I wouldn't be able to fly both. The two aircraft are based with two different schools/clubs and to hire both I'd need to pay two annual subscriptions. It's not a huge amount (£120 in each case), but I'd rather avoid it if there is little to no benefit.
I am aware also that there are more ideal aircraft with regards to this matter, but as I am in no position to join a syndicate/group or buy outright, I have no choice but to hire from schools/clubs/FTOs etc and that means I am restricted to the typical PA28/C172 aircraft that they tend to use.
I think I'll ask around a bit more before making a decision. If it is worth it, I may end up deciding just to put up with paying two annual subscriptions and simply use the PA28 when I'm on my own and the C172 for flights with passengers.
Thanks again for all the input.