Would there be a difference between boiling whole black peppercorns or fine ground black pepper in a stew? When putting whole black pepper in a stew e.g. curry, am I right in thinking that they completely dissolve because I don't remember seeing any in the finished pot or dish.

I was reading alternatives to using chilli and black pepper was listed so I thought if I want to try it, maybe I should make a fresh ground black pepper then add it in the same way one would add chilli powder.  

However it has occured to me since whole black pepper dissolve in curries, what would be the point fine grounded black pepper to replace chilli, wouldnt the fine black pepper just dissolve too and hence you may as well use whole ones as you will end up with the same result/flavour?
Well, I've never had whole black peppercorns dissolve.  In very long cooking, and depending on the variety and age of the peppercorn, they can soften somewhat.  But when adding whole peppercorns to a dish, I either plan to remove them after cooking or be prepared to bite into a serious bit of pepper every now and then.  To avoid this problem, I generally at least "crack" or crush the peppercorns a bit if I intend them to be in the final dish.  (This aids in softening and seems to allow the flavor to blend a bit more, though large bits can still be very peppery.)

Black pepper tends to lose a lot of subtleties of flavor quickly once it is ground, which is why pepper grinders are so common in restaurants (and at home).  There's no advantage of using pre-ground pepper in a soup or stew, but I definitely tend to grind it myself right before adding to avoid the large chunks of peppercorns.  (Different varieties of peppercorns can vary a lot terms of potency, especially when they are fresh, so perhaps yours are more mild than the ones I generally use and thus less noticeable when in larger chunks.)

Some people buy pre-ground pepper and find it convenient, though.  My one caution, if using pre-ground pepper and you desire a very peppery dish, is to not overdo it.  Whereas whole peppercorns will gradually release subtleties of flavor, pre-ground pepper can change somewhat quickly from barely noticeable to a burst of strong pungency.