eyeinthesky - You can use an electronic calculator in JAR CPL exams, like I said they're just a subset of the ATPL's.
You are right about taking an ATPL course if you want to be more than a paid instructor/glider tow pilot/para dropper etc.
you wrote;
'If you do the CPLs and then want to upgrade you'll end up doing the same stuff twice'
although this is true right now (and bloody stupid...JAR arrgghh)I understand some flight training organisations are talking with CAA, about changing this so you get a full credit for CPL theory, which would make more sense.