1970's wiring

We came across some unearthed lighting cable installed in the early 1970's.problem when certification.After installing a new consumer unit.R1+R2 a problem.R2 ok.RCD operation compromised.+ Lights up & down have to be on same side of board.Because of two way switching.No compromise in 17th edition Regs.would be better off if a 16th edition board was installed.what is your comment's.Interested hear them.