Just be aware that there is no level two in the Scottish Vocational System so you will need to sign up for an SVQ level three. They should expect you to have an employer as it is not a qualification that can just be taught in a college environment, it needs workplace evidence too.
Don’t be fooled into thinking that because there are no qualification requirements to call yourself a plumbing and heating engineer it is easy. Anyone on this site will tell you it is hard work and you have to be good at it all the time if you are going to make a good living out of it.
Word of mouth by customers can be bad for business as well as good particularly if they are tell their friends that you are incompetent, bad news travels much faster than good.
Be very careful about just becoming gas safe registered as you will need to be able to connect a gas boiler to the wet system and if you have little or no plumbing skills you could find you are not able to operate competently and therefore make a reasonable living.
If you are serious about this becoming your career for the future you will find that there are plenty of professionals who are passionate about good standards who will want to help, but only if they think you share their passion and are treating it professionally too.