Hi,
If you're searching for a reputable breeder I wouldn't begin searching in the trading post or speaking to people in a pet store.
A good, reputable breeder (opposed to a backyard breeder or puppy farm) will generally have a waiting list for their available puppies and will ask for applications from potential owners to ensure suitability.
http://www.dogzonline.com.au/breeds/puppies/british-bulldog.asp is a good start. The site generally features puppies from registered breeders.
British bulldogs are rare and for that reason expensive. Expect to pay around $3k - which if you think long-term isn't a bad investment

They will live for 10-15 years, provide unlimited love, loyalty and laughs.
I'm not sure how much research you've done but being brachycephalic (flat face) means they cannot be exerted in hotter climates (they struggle trying to regulate their temp). They'll also likely need regular attention to their skin folds - especially on the face.
I own two pugs - pretty much our fur children. They have similar characteristics to bulldogs, just much much smaller.
Have you considered French bulldogs? Their kind of a mix between British bulldogs and pugs - they have bat ears. Tough looking little dudes but also cost a packet.
Best of luck with your search - remember its a long term commitment.
Jamie