I see that you are employed by a JIB firm, so unless things have changed they should register you for a grade card. The grade is based on your quallies and experience. The object of these when they started was to set standard rates of pay , we tended to move from firm to firm in those days , so you present your card and they had to to pay you at least the minimum rate for that grade .
Also the new firm could gauge your skills level , as an Electrician Grade , Approved Elect. or Technician Grade . There was no need for the CSCS stuff , it was already in place .
If I were you I think I'd try to get at least an Electrician Grade card if you intend to be working for JIB firms , or they'll keep you on the lower rate of pay.
Although I'm self employed I have kept mine going , use it mostly as an ID card TBH.