ummmmm, which pug puppies on that page??
I don't know how the prices are in the UK, but in Australia, $800+ is a reasonable price to pay for a pup from a registered, non-puppy-mill breeder. (think this is about 250+ pounds). You would expect to pay up to double this for breeding/show quality pups (not necessary for a pet pup, only if you are a breeder/showie).
Make sure you get a pup from a breeder where both parents are available to be viewed, and both parents have been Penn hip and elbow scored.
Expect a happy, confident, laid back attitude from the breeder and both the puppy's parents.....don't listen to the breeder if they say:" oh, she is only growling to protect her pups", or "he's just defensive with strangers"....unless you want a vicious attack guard dog, you are better off keeping on looking until you find a pup where both parents are relaxed and friendly- yes, even with strangers around their pups! Just makes life easier in the long run.
best of luck with the new baby, keep us posted!!!