Your problem isn't going to be that you up against people with qualifications, it's that you're up against people with experience. You stand a high chance of getting caught in catch 22 of not being able to get employed as you have no experience and not being able to get experience as you can't get employed.
The problem with these fast track courses is they don't give you any real hands on experience. What practical stuff you do is based in unrealistic scenarios in the training centre work shop and even that you don't do much of.
They can be ok if e.g. you already have hands on experience with plumbing but want to move over to gas so need qualification. But even then you'll still need to try and do the various manufacturer courses afterwards to get more knowledge and ideally also spend some time helping out someone already in the trade (the really difficult thing if you don't have personal contact) and you're still realistically looking at going into self employment which is really hard work, not much security for first few years while you're setting up.