I did my General Certificate back in the mid nineties after 20 odd years on the spanner and 6 or 7 before that doing other site jobs.
I did a 2 week intense course, which having been out of any type of schooling for 25 years or so at the time, i found really difficult, but i managed to pass first time thankfully, as i couldn't afford to do it all again at the time if i failed.
It was difficult to get a start in H&S afterwards, because as others have pointed out, all the companies wanted someone with some background experience.
I couldn't even get back into scaffolding management properly, as companies made comments like "Oh, you have scaffolding and health and safety qualifications. Isn't that a conflict of interest ?"
After a couple of years i got called by an agent who needed someone in Oman for an up to 3 month only, end of project HSE supervisor with scaffolding knowledge job and although i wanted something longer than that, i took it.
It's this type of start you need to be looking for, either in the UK or abroad ie, filling in where no one else wants to. This first 3 months led directly to me being kept on by the company for their next project in the UAE which lasted 2 years and with that on my CV, i have since travelled and worked all over Europe, North Africa, UAE and now the Far East and have earned some excellent salaries.
Just take anything that will get something related to HSE supervision on your CV, even if it is only as a supervisor/oficer/advisor. It's just like starting in scaffolding, you cannot jump in directly at the advanced level, you have to work your way up.
I also went through and am still going through the pangs of having to tell people not to do things that i did quite normally many years ago, but there is a way to do it and explain the reasons why and unlike some 'straight-out-of-college' HSE qualified people, we with previous site working knowledge should be able to explain how things have changed and companies perceptions of what is acceptable and what is not (manily for legal reasons normally), have changed. Because of our previous working experiences, we can also assess the actual risks of perhaps being a little bit flexible in certain circumstances, whereas the guy straight out of a perfect college environment, where everything is taught as being either black or white, with no flexibility to be allowed, can actually be a hindrance on site in highly pressurised construction schedules.
My advice is to go for the General Certificate and take it from there. I've never done the Diploma, but have to say that there have been a few positions that have been denied to me in the past because i do not have it, particularly overseas, as many countries now seem to want a degree in place before they will grant a visa to the company that wants to employ you.
One way out of that is to do what many of the Indians and Pakistanis i've worked with in the Middle East do, and that is to buy one online, but they are easily spottable if anyone really looks and again, it's something i would not do myself, or advise others to do.
As for HSE Managers/Advisors being hated, some do take this stance against you, but a sense of humour helps and spending time having the craic with the lads during your daily contact with them, normally eases any tensions and it is only the odd idiot who really rebels aginst you and what you are trying to do, which is really only protecting them and others from harm. Those types you can well do without anyway and if they will not make any effort to join with everyone else in doing things safely, then you are probably better off without them being around.
Good luck anyway.
Cheers,
John.