Mandy, although they are available I would give the bareback pad with stirrups a miss if I were you. Obviously, you can't use the stirrups when mounting because the pad will slip. Once on board, if you become unbalanced and put more weight into one stirrup than the other, again, the pad will slip. The natural build of your cob won't help matters either as he is probably more round than narrow (I've got one too!).
More importantly, the way the stirrups are attached to bareback pads means that your weight is not distributed evenly across the horse's back, unlike stirrups on a saddle. This can make the horse's back sore.
I gather from your previous posts that you can feel trapped in a conventional saddle. Have you looked into some of the treeless saddle designs? Perhaps something more stable than a bareback pad with stirrups but not as rigid as your current saddle?
I have a bareback pad (no stirrups) and would recommend it. Plus, I have a treeless saddle for the cob as he is built like a barrel on legs