A combined CPL/ME is cheaper than doing a SE CPL and MEP providing you pass first time in not too much over minimum hours. You are saving an examiners fee (although an MEP fee is only 150 or so, not a full CAA charge of 600+).
A combined CPL/ME course is infact 28 hours training, where as a SE CPL + an MEP will be a minimum of 25 + 7 hours (32 hours).