You can do the MEP(L) rating right after PPL; I did (a few years ago). You do need 70 hours PIC. Remember that you would have to contend with both a complex (variable pitch prop, retractable gear) and a twin at the same time. Quite feasible, but it might take you more hours (and therefore cost more money) than doing it as part of/after the CPL, ie. after you got to grips with a complex single. Also, the MEP(L) validity is one year, so you might end up having to renew it before you pass the ME/IR.
Cheers
