Thank you everyone!
Cost isn't the issue, there's no significant price difference between flying the two different aircraft. The cost might come in to play if i need extra training because i've confused myself or something along the lines of such.
Flying the PA-28 is not necessary but it's certainly enticing!
I've had a look at the checklists and manuals for the PA-28 for comparison and there doesn't seem to be all that much of a difference, in the manner of what the checklists involve, Vr is the same but things like BROC are different etc.
Although, taking into account how different the controls are in both aircraft as i've looked at different photographs of the PA-28 and compared it to the C152 and obviously they're quite different - That might be the challenge. I perceive the challenge as fun, however, i am training so fun can be reserved for a later date!
I'm very happy to be patient and wait until later on in my training to try the PA-28, as the majority of you have suggested. It's been great to get some perspective on the subject.
It was initially an instructor that planted the seed for thought. So i'm assuming i'm progressing competently enough to be able to fly the PA-28 at some point, but after some thought and having done my research, i'd prefer to wait until i've at the least surpassed my GFPT.