What are the requirements to work in the artistic field (voiceover/acting) in the United Kingdom?

Hi !
I'm a voiceover artist and also a kindergarten assistant Italy.
I saw an job proposition on Starnow for a voiceover part in the UK (Birmingham) and I don't really know what are all the requirements... I know about Actors Union, Equity, I know about the visa and I am looking for an agent in the United Kingdom. Other than that I don't really know what else to look for? And especially mention in my cover letter. I'm not a green artist here but in the United Kingdom it's a whole other story, same for every country !
I know it's a matter of time and patience and if not this job maybe another but at least get an idea? I have money put aside and I am ready to go if I have the opportunity. With all the Brexit mess and the Europe who doesn't want to help too it's almost taboo to ask.
I have credits and can get recommendations from my schools, colleagues and my former agent that isn't a problem.
My former agent doesn't know she wasn't the nicest lady on Earth and she was really old school (everything was on paper and she hated the informatics) she is now retired. And I had to put on hold to take care of my grandmother so a job, an activity plus taking care of her was a lot... Now... well it's a bit why I want to leave... Anywho I digress ! Is there anything I need to know?
What are the requirements to work in the artistic field (voiceover/acting) in the United Kingdom?
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