"Average salaries are higher among professionally registered engineers in all areas of industry, according to a 2018 Salary Survey produced by The Engineer. The mean average salary among professionally registered respondents was over £8,000 a year higher."
https://www.theengineer.co.uk/professional-registration-engineer-salary/
Salary survey here
Moshe Waserman BEET, MCGI, CEng MBCS, MIET