My border collie is 6 months and will not shut up! Ive had him since he was a baby and he has been well socoilised and trained, he never used to bark at things, but now he barks at other dogs/people, strange objects, ive tried teaching him speak/quiet to no avial, im tearing my hair out over this, any suggestions PLEASE

Does he do this at home? On walks? When he's alone?

When my dog barks at things I don't want her to, I call her to me, ask her to 'sit' 'down' and then give her a reward and send her on her way - this distracts her from whatever she was barking at.....

Hi,
Our puppy barks at us if she wants to play. or to get our attention!.. have you tried totally ignoring the barking if its doing it in the house..what about hand gesture for 'QUIET' and then treat..eventually you should just be able to say the word 'quiet'- though you did mention that you had tried similar things like that though...mmmm..mabye try to think 'why' your dog is really barking?..are they frightened, hungry, wanting your attention, or being aggressive?..if they are barking in an aggressive manner..personally I would contact your vets to refer you to a 'good' behaviour specialist.
I know you must NEVER shout at a dog when there barking..as they only think your barking too!!!! You must try to be firm and consistent.
Im no dog expert, just going off what we ve tried for our little one.  Now if she barks at us....we shut ourselves into the kitchen for a few minutes..failing that we calmly put her in the kitchen for a few minutes.  If she then continues to bark when she comes out.. she goes back in! (thats if we can catch the little tyke as she sprints round the room thinking its a game of chase!!!!).
Persevere..and sorry I couldnt be more helpful.. but if no one else can offer you any advise that works for you..I would strongly advice you chat with your vet who may be able to help!   Good luck!