my pup is now 17 weeks old and was coming on well with the mouthing and the "owch" method was working .... all of a sudden she just carries on and bites quite hard i then tried walking out of the room so she losses her playmate so to speak to no avail, i have  2 year old and she is getting to be face level with him now when she jumps up so could easily bite his face (i know she wouldnt mean to ) , my other 2 children aged 4 and 7 know to turn their backs to her when she jumps up (not that that stops her ) but the baby dosnt , i let her off the lead for the first time yesterday and she did well came when i clapped and shouted but was a bit confused about "fetch" , i took her again today and she just kept using my trousers as a tug toy :/ again i tried the owch method she ignored me so i tried distracting her with her ball and that never worked either ..... she will be going to training in the next week or 2  (she was booked in but i couldnt find the venue by the time i had the class was halfway through then i got a big sky bill through so couldnt afford it .. should of paid in advance :( ) this is the only bad thing i can say about her really she is fully house trained sleeps in a crate with no fuss , gets on well with my other dog and tollerates (if not torments) the cats and will sit on command for a treat , so if i can fix this she will be perfect ..... i also have a housetraining line i use to stop her jumping up and reward her with a treat when she sits , where am i going wrong lol?

Sounds like she's just starting to chance her arm a bit now that she's getting older.

The methods you're already using sound good, and I'd keep them up.  Perhaps try to find something even more interesting as her distraction - a squeaky toy perhaps?  A tasty treat?  (But only given to her when the desired behaviour is happening of course).
Keep persevering is all I can say, they can be stubborn little monkeys! 

It might sound a silly question, but does she know you mean it when you say 'ouch'? 
Even now, both of mine know the difference in the tone in my voice & therefore know when I actually mean something or not!
I've found with Staffords in particular you have to be quite forceful (not physically obviously), to get through :)

Is she nippy with your other Stafford?  Does your other Stafford tell her off?

Have a little read through this http://www.cockersonline.co.uk/discuss/index.php?topic=64170.0;wap2 The Bite Stops here by Ian Dunbar. 
Some really useful tips, but also an explaination as to why bite inhibition is so important.

Keep at it! 

i really squeel it as a pup would , she does push her luck with my other stafford yes but she soon submisses and rolls onto her back when tia growls at her , i suppose i just forgot how much hard work they can be when pups lol she is such a character and looks up at me with her big round eyes like butter wouldnt melt sand then jumps up all teeth haha ..... and on a different note i recieved her HC results today and she has tested clear just waiting on her L2HGA results :)

the squealing method works with very young puppies,b but certainly in high prey drive dogs, terriers and the like it will actually excite and encourage what to them is a great 'game'.

As for your toddler she should not be allowed around the pup when it is playing, puppy is just like her in that it does not understand that it can hurt the flimsy human puppy.

Put pup behind baby gate when toddler is running about, pups especially staffies which I like to canine cannonballs play too hard for a toddler not to get hurt by accident, and as you have.

There are some great articles on this site: http://www.dogstardaily.com/ and for this issue this article: http://www.dogstardaily.com/training/teaching-bite-inhibition and also this new article: http://www.dogstardaily.com/blogs/dogs-and-children%E2%80%94safety-rules-and-preventing-rather-curing

ditto Brainless... I was just going to say the same thing.  A squeal will set a Stafford right off!  Ooh fun and games time :)

(Plus some great links there too for you Ash).

Perhaps try a very firm 'hey' or 'no' or 'ah' as opposed to a higher pitched noise.

Just thinking out loud here really... if I'm saying something like 'oh Alfie get dowwwwn' in a sort of don't-really-mean-it type tone of voice he pretty much ignores me..
However, if I say 'Alfie- OFF' in a much more matter of fact type voice (not shouting just firm) - he responds immediately...

Reminds me of my piano lessons as a youngster - 'once more with feeling' :)

(glad to hear positive news re: HC results)