"If anyone is doing gas work in the United Kingdom, and they are not Gas Safe registered, they could be working illegally". Gas Safe
You cannot just train for LPG on boats. You need to do Gas Safe before you get to LPG and still further training for boats. This is a big time sacrifice, never mind the financials! Follow my gas safe training from Jan 5th 2019. Theory/workshop takes 8 weekends in Cardiff, Followed by 4 weekends on job portfolio, Then, the ACS exam that gets to Gas Safe. Then LPG!