'work in the energy/oil/gas industry' is vague
What area?
or do you just mean to go in as a roughneck?
I am a time served welder/fabricator, started off in heavy engineering and then went offshore on shut down work, where production platforms would undergo work not normally able to be done when they are "live" and producing oil.
I then had a stint as drill crew as a roustabout, then roughneck. It was good fun but hard graft, also factor in, that the drilling industry was going through it's first real crisis and Maggie Thatcher was crippling the miners and anything trade union orientated, so it was never going to last for long and the money was rubbish.
I then went back to engineering, went back offshore as a night shift supervisor and hated it. I took one last job offshore as a shift superintendant, which was a great job, lasted about a year and got a promotion back to the beach.
I started working for a local engineering company in 2004. They liked the way I worked, the clients loved my safety record and they offered to put me through my NEBOSH exams for the job I now do, which is Senior HSE Advisor for a company which specialises in sub-sea oil and gas producing structures.
I may be able to summarise in a couple of paragraphs, but this was 30 years of graft.
Do you have a background in any particular discipline or trade, that will be the direction to go if you have. If not, tackle the drilling companies and see if you can work your way up.
Be aware that the UK offshore industry is on the bones of it's ar$e at the moment, so jobs are not in abundance.
Good luck to you though, and I do hope you get a break.