I must ask the previous 'posters'. Do you think this is funny? Or degrading?
The guy has a dilemma, and I guess he came on here to get some answers from some helpful plumbers. Instead one guy has a cheeky dig and the rest jump on the band wagon.
Before I attempt to answer his question I'd like to take the opportunity to comment on the fact that there are several grammatical errors in your posts. Helpful? Nope. Lame.
Anyway. It's my understanding mate that there is little difference between the two. The 6129, as you said, focuses more on domestic plumbing. The 6128 doesn't focus as much on lead work and roofing and is also a bit more commercial and industrial than the 6129. Other than that I do believe that they are equally capable of making you a qualified plumber (i.e both give you the opportunity to gain an NVQ level 2).
The problem you will find is that, the organization is biased toward the qualification that it is providing the training for. So if you ring up, say the Plumbing Academy (Kent), they hardsell you the 6129 like its the only industry recognized qualification to get you in to plumbing. New Career Skills provide the 6128 in Sussex, they say the 6128 is just as sufficient as the 6129, but it also allows you to specialize in Heating & Ventilation.
I thought it would be a good idea to ask plumbers themselves. Some will tell you that these fast track courses are a waste of time and money, and that if you want to be a good plumber then you need to go via a college/apprenticeship route. I figure they say this because naturally they want to protect their trade. And some will be annoyed that they spent 4 years learning something that now you can pick up in less than a year. I have a plumber that lives on my road, I went and spoke to him for the first time the other day and that's what he was saying.
I definitely do agree though, that no-one should expect to come out of a 12 week plumbing course like they know the trade inside-out. That would be foolish. Im sure it will take years before you are fully confident you can tackle any problem.
I'm not disputing that some of the organizations do in fact just want your money. Read the 'Course Feedback' section of this forum and you'll find that out yourself after several minutes of reading. But, if you cant be bothered with college, or you are too old for it, or you have bills to be paying, then what other option is there than to splash out £5000+, really?
I was in your boots not too long ago. Opted for the 6129 in the end. Mainly because my goal is to be a self-employed residential plumber. So there you are. Make sure you think about about it wisely.
Hopefully that helps you mate, and hopefully other people can give you feedback too.
p.s yes I did make the extra effort to make sure there were no spelling and punctuation mistakes in my post.
