COA (certificate of approval) is so called 'security licence'.
It is easy to get a licence, visit the 'Ministryof Justice', fill out a application form,
and apply it with fee. That's it.
It will take more than a month because they will check applicants' criminal records.
It will be issued if you don't have any criminal record.

There are some security courses, Level 2, 3, 5, but these are not compulsory to get a licence. Most security companies offer free Level 2 course for their employees. this course takes about a year.
Over Level 3 courses take several months, but you should pay for it. I think these courses are full time studies. I know some good companies only hire someone who has level 3 certificate.

If you are looking for a security position without certificate, Frist aid course could help, I think.
At first, you can do as casual... have some experience... then ask for a full time position.

If you ask the security job is good to work.... all depends on the site where you will work... some sites are really horrible than you think...

Thanks a lot for your information.
I wish you have great day today.~~~