
There's no reason for you not to ask for pick of litter if that's what you want. Make sure you get any agreement in writing, signed by both parties, before you go ahead.
I gather that bulldogs are not the easiest of breeds to mate, so I hope either you or the bitch owner has handled a bulldog mating before.
Another thing to remember is that
you as well as the bitch owner will be morally responsible for the future of any puppies sired by your dog, and must be prepared to take them in for rehoming at any stage of their lives.