Hi, You need the City and Guilds 6129, once you have this gain some experience with your plumbing friend then you can be assessed on site for the city and guilds 6089 (NVQ2) approx 5/6 assesments, you will then be a qualified plumber. Getting some on site experience is the hardest part so if you know a plumber who can give you experience that is the main thing. Make sure who ever you do a course with includes the 6089 (NVQ2) assesments in their course as well as the technical certificate 6129. You are probably looking at £5000 - £7000 for a fast track type of course. Do not be fooled by courses that offer the 6022/6032 courses they don't mean anything in the plumbing world! OCLI Plumbing do the 6129/6089, you study the theory at home then go on workshops/assesment days, these are from 1-4 days each workshop and there are quite a few to do. See
OLCI Plumbing Courses make sure you know how much everything will cost in total. Also have seen VIY Plumbing training which costs £6580, and includes the 6129/6089, however this is one 10 week block so you would have to leave your job etc.
Hope this helps.